Heres a full description on how you can protect your computer from viruses, and keep em off.
A short Introduction:
Many people have various issues with their computer - it's running too slowly, games aren't working, pop-ups appearing out of nowhere, internet connection going to the dogs, etc. But where many people go wrong is having too much trust in themselves and their PC - people think "Oh nothing bad will ever happen to me" and also largely think "A PC can take care of itself". It will happen, and your PC can't.
The following steps are things that may seriously help your PC out, and anyone who has never done these things before should do it - be aware that a lot of this is largely directed at Windows XP Professional & Windows 2000 Professional, but anyone with a Windows machine can use most of the advice in here (just some menu options etc. may be slightly different).
Do note that some of these steps involve you closing down all running programs, including your web browser, so either ensure you have a good memory, or print this out if possible (or try to do some fiddly browser loading/closing with this page bookmarked between each task). By "All running programs", this includes things such as: MSN, Internet Explorer, Mozilla, Opera, IRC, Winamp, Media Player, Outlook Express, AIM, Yahoo Pager, Skype, Kazaa etc. If you don't close these things down, then it will prevent the "spring clean" being fully effective, and you may as well just not bother.
Now. Onto the nitty-gritty.
Step 1 (cleaning old temporary files, cookies, history):
The first step in doing a "Spring Clean" is to remove all temporary files. To start with, go in to "My Computer", right click on your "C:" drive, choose "Properties", and from there, click on "Disk Cleanup". Now for some people this can take a long time, even up to half an hour - so be patient.
Eventually you'll have a list of tick-boxes, tick everything in here, click "OK", and again wait for it to finish.
Note Windows XP users: Did the "Disk Cleanup" freeze up completely on "Compress Old Files"? Taken longer than half an hour and still not doing anything? You may need to reboot your PC, then afterwards, follow these instructions, before trying again:
(You may want to back your registry up before doing this)
Start -> Run -> "regedit" (without the quotes) and hit the Return key.
In registry Editor, locate through the "registry tree" to this location:
HKEY_LOCAL_MACHINE -> SOFTWARE -> Microsoft -> Windows -> CurrentVersion -> Explorer -> VolumeCaches
Right click on the "Compress old files" registry key, and delete it. Try the Disk Cleanup again now.
For Internet Explorer users: After this, come back to/load up an instance of Internet Explorer, click on "Tools" -> "Internet Options" and then the "Clear History" button at the bottom. Now click "Delete Files", tick on "Delete All Offline Content" and click "OK". Next click "Delete Cookies" and "OK" again (be aware this will mean you need to log in to any sites that previously had you "Remembered" - but is worth doing as many computers, especially on older versions of Windows, gain "corrupt cookies" which can cause all kinds of problems when browsing - though this only seems to happen with Internet Explorer).
For Firefox users: It's a good idea to clean the 'cache'/'temporary files' Firefox uses in your day to day browsing. Within Firefox, select the Tools menu, go to "Options". Here, select the "Privacy" tab at the top, and then select the "Cache" tab. Click the "Clear Cache Now" button, and click Ok.
Any other browser users: Check your browsers help files to find out how to clean any temporary files/cache etc. with your browser version.
Step 2 (removing all your old games & programs):
Now you need to uninstall everything that you don't want any more, or don't need any more.
Be ruthless here - do you really play that game so often? Do you really need that application which simply saves you pressing 2 keys?
Go to your Start menu -> Run -> "control panel" (without quotes), and choose "Add Remove Programs".
Uninstall everything you no longer use, want or need - if there's anything that you aren't sure what it is, try searching for it's name on Google and find out. Next go through your entire "Programs" list in the Start Menu and check for any uninstalls here (because not everything shows up in Add/Remove Programs) and delete any "Empty Directories" from your start menu (some uninstalls leave directories in your start menu, or if you have uninstalled games incorrectly in the past - eg simply deleted them without uninstalling - there may be traces of the game/program here - delete everything that is no longer installed but still shows in the menu).
Step 3 (get rid of all that spyware and adware!):
This step requires you to download a few pieces of (free) software that will aid in automatically removing a lot of "spyware", "adware" and other general nasties from your computer (not the same as viruses). It is advised you download and install all these programs first, then put your computer in to safe mode before actually running them. Instructions for booting in to safe mode can be found in the link at the bottom of this step.
First, head on over to;
http://www.safer-networking.org/en/downl...
Download & install "Spybot Search & Destroy v1.4" (if you have any older versions, uninstall the older versions first). Now run Spybot Search & Destroy, "update" it (from the main window of SS&D, choose "Search For Updates" - get the updates one at a time, not all at once, to avoid problems)... once updated, you can close the program. We won't do any scans until we have all the programs in this step and are in safe mode.
Now go on over to;
http://www.lavasoft.com/products/ad-awar...
Download and install "Ad-Aware SE Personal v1.06" (2.72Mb) by clicking the big "Software" button in the middle of the page which will take you to the download.com site to download it. Once downloaded and installed, start up Ad-Aware SE Personal and "update" it's definitions files by clicking the "Check for updates now" link or the "World" icon in the top-right corner. Wait for this to finish, then close the program. Again, we aren't doing any scans with these programs until we have them all and are in safe mode.
After that, get Advanced Windowscare V2 Personal from here: http://www.iobit.com/advancedwindowscare...
Nothing to update here, it's just run and go. Don't run it yet, as stated above.
Finally, we want a more specialist application just to cover a few more possibilities - CWShredder. Download this application from here:
http://www.intermute.com/spysubtract/cws...
You just need the free "stand-alone version of CWShredder" from this page. Note that this program does not need installing - simply download it in to your C: drive or somewhere easily accessable from safe-mode; it is already in a "ready-to-run" form.
Now that we have all 4 of these applications, and they are all up-to-date versions with the latest spyware definitions, you need to boot your PC in to safe mode. Instructions on booting in to safe mode for various Windows versions can be found on the Symantec site here:
http://www.pchell.com/support/safemode.s...
Though for Windows XP/Windows 2000, you should be able to access the boot menu by tapping the "F8" key on your keyboard while your computer boots up (needs to be before the "Windows loading screen" appears) - it should bring up a text-based menu that allows you to select "Safe mode" at the top. Please make sure you log in to the user account you actively use in normal mode, rather than any listed "Administrator" user, eg if I booted in to safe mode I would log in to "Ace" not "Administrator". Don't be alarmed by everything looking "Big" - safe mode is very limited and so your screen-resolution will be low.
Now that you are in safe mode, first load CWShredder from wherever you saved it to earlier (eg "My Computer->C:"), and once loaded click the "Fix" button at the bottom. Let this run through (it doesn't take very long), and then click "Next" and "Exit".
Next up, load "Ad-Aware SE Personal" and click "Start". Select the "Perform full system scan" setting and hit the "Next" option. It is generally advisable to fix every entry found in Ad-Aware SE. Exit Ad-Aware once everything is finished (once it is fully scanned and everything has been checked and "fixed").
Thirdly, open up Spybot Search & Destroy and click the "File" menu, and choose "Search for Problems" and wait for it to scan your PC (be patient). Once it has finished, click on "Fix Selected Problems" at the top and hit "Yes". Close the program once finished.
Finally, open up Advanced WindowsCare v2 and click "Start Scan" at the bottom. Let it scan, and do its stuff, then fix the problems. This will clear up your registry of anything out of the ordinary, and also protect your files from being infected with spyware in the first place. Nifty, eh?
Now this may sound like overkill, but I highly recommend that you now re-scan with the above 4 programs in the same order - I personally (as have others) had experiences where certain types of really really nasty spyware can hide itself so deeply that the first scan of the above programs is like peeling the "outer skin" off them, and only the second scan actually killed the spyware itself. So if you are having any particular spyware problems (popups appearing randomly/while browsing sites you know don't have any popups would be a good sign), please run the above 3 scans again, in their full, before proceeding.
You can now restart your computer back in to "normal" mode.
Note: If you already have HiJackThis from the below step, and are very experienced in it's use, it would be advisable to run it at this stage (whilst still in safe mode, immediately after the above 3 spyware scans) and remove everything "bad" now. Anyone inexperienced at HiJackThis move on to the next step.
Step 4 (HiJackThis):
NOTE: This step is completely optional, and is only recommended if you have plenty of free time with Google or a pretty safe foundation in terms of knowledge of the applications.
Step 4 is where things might start to get "complicated" for the uninitiated, but help is at hand. You need to rid yourself of the worst of the spyware/adware on your computer, and also while you're at it dispose of all "pointless tasks"
(for example programs like "QuickTime", "WinZip", "WinAmp Agent" might be useful on your PC - but you do not need them always running with an icon in your bottom right task bar - they'll run fine without these).
Now really, for Step 4, the "safest" and most reliable way for you to do this, is to seek outside help, so here's what I recommend... Head to:
http://www.spywareinfo.com/~merijn/downl...
Scroll down the page to find "HijackThis" select any mirror and "unzip" it somewhere sensible (Such as "C:\HiJackThis\") so that HJT can create backups.
Close all running programs and locate & run HiJackThis, click on "Scan Now", and then click on the "Save Log" button (formally "Scan Now"), save it somewhere (such as on the desktop), open the log, and then scan through it. Look for things that sound odd or unfamiliar; if in doubt, Google it. You could try PMing it to me, and if I have the spare time I'll look through it for you, but if you want to be self-sufficient with HJT, it'll take some time; patience is a virtue.
Step 5 (Windows XP users - get rid of possible popups!):
Many people new to Windows XP and not protected/hidden behind a router will experience "pop-up adverts" that aren't in a browser window, but are actually in a "normal looking" alert box (but advertising things like "buy your diplomas" etc. Even if you don't, but you use Windows XP, you should still check that "Windows Messenger Service" is disabled - note that this is not the same as "MSN Messenger".
To check/disable, click on your Start Menu, Click on Run, and type in "services.msc" (without quotes). You should now have a large list of "services" within your PC. Scroll down to "Messenger", and double-click on it. Near the bottom, if the "Services Status" says "Started", then click "Stop" (row of 4 buttons along the bottom - "start stop pause resume"). Now under "Startup Type", select "Disabled". Click "Apply", then "OK", then close the services window.
Step 6 (get a decent virus scanner!):
Now, there's many different virus scanners out there. But... unless you currently run either "Avast", "AVG" or "Norton AntiVirus 2006 Professional", then I say this to you: Uninstall your current virus scanner. Go on, remove it, kill it, say bye bye. "Bye bye old virus scanner!". That's it. And in with the new... totally free, and nicely powerful, with frequently updated "Auto Virus Library Update" abilities. Head on over to:
http://www.avast.com/eng/download-avast-...
Click the "Download" link on the right hand side. It's a completely free anti-virus package, and only requires you to sign up to use for more than 60 days!
Once downloaded, install it, and then go through the options so they suit you (make sure anything involving "Auto Update" is on), and choose to "Update" it on the spot so it is entirely up to date. At this point you should boot in to safe mode once again (see step 3 for instructions), and within safe mode, open up Avast manually and run a complete "Scan" of your entire system. Once finished, let it try to fix, and if not quarantine/remove all the infected files it finds (if any). Remember: All Anti-spyware and anti-virus applications are far more reliable in safe mode, as safe mode can help to ensure nothing is running in the background hiding itself from the scanner.
Step 7 (update your Windows!):
Possibly the simplest step of all, with the only complication being this before you start: Disable any proxy server you are using in Internet Explorer. Broadband users open Internet Explorer, head to "Tools" -> "Internet Options" -> "Connections" -> "Lan Settings" and un-tick "Use a proxy server". Hit "OK", then hit "OK" again, and close down your web-browser.
Re-open it again and head over to;
http://www.windowsupdate.com/
Click "Scan for Updates" - if a security warning pops up, hit "Yes" (one of rare, rare few sites that you should ever hit yes to a security warning while web browsing - anything else is probably evil spyware, adware or viruses). Get all Critical Updates found, and reboot your computer. Head back to http://www.windowsupdate.com and repeat the process (get all critical updates and reboot). Continue to do this until there are no longer any critical updates to obtain.
Step 8 (driver updates...):
Updating drivers is a huge topic, and one best suited to Google - however, some quick advice I can give is:
Drivers you should update relatively often, or when doing a "spring clean" are: Motherboard drivers (NVidia NForce, Via Hyperion drivers), Soundcard Drivers (fairly often Soundblaster, though there are many other common soundcards built in to motherboards these days), Graphics cards (more than likely NVidia or ATI). If you don't know what make/manufacturer/model any of your hardware is, then a great free utility for finding out just about everything you need to know about your computer is "Everest" by "Lavalys", available here:
http://www.majorgeeks.com/download4181.h...
Note: The official Everest site no longer offers the free version for download, and if the above link stops working you should Google for another site that offers "Everest 2.20" for download, the last ever free version of the great application.
Step 9 (secure yourself further with a software firewall...):
In the modern day, absolutely nobody should be without at least anti-virus protection and a software firewall. The importance of a software firewall is valid both for those "directly connected" to the internet, and also to those that are behind a router or other advanced network setups, as a software firewall can both protect against incoming "bad stuff" but also control your computers outgoing "bad stuff" (something a router won't do). First disable "Windows Firewall" if you have it enabled (often enabled by default on Windows XP Pro), and uninstall any other software firewalls you may have (many out there aren't capable of doing a secure enough job, or can be unstable and cumbersome, such as ZoneAlarm has become of late). Then you need to get yourself a free copy of Sygate Personal Firewall from here;
http://www.filehippo.com/download_sygate...
Install and reboot if directed. Now when any software tries to access the internet for the first time from your PC, Sygate will pop up a message asking you if you wish to "Give It Permission" - you can tick a box "Remember my Answer" (or similar), and either choose "Yes" or "No".
When do you choose Yes or No? Firstly read the message Sygate pops-up and try to identify the application - sometimes searching Google can reveal answers on what an application is - and make your decision on that... plus if you've just opened up a program that you know should be going online, eg you've just opened up MSN Messenger for the first time, then most likely you click yes. If you've just downloaded a piece of software that you're fairly sure should have no need to go online, run it for the first time and Sygate instantly pops up, then consider clicking no. If things don't work as they are supposed to, you can always later change these "permissions" by double-clicking the Sygate icon in your task-bar and clicking on "Applications", and modifying each programs "permissions" from here. Also note: "Notifications" such as apparent "incoming attacks" or similar - 99% of all of these will be totally "Safe" - ie not really a big mean hacker coming to attack you, and will only get you needlessly paranoid that everybody is out to get you. Therefore you should always disable any "alerts" in Sygate and just let it do it's job silently in the background, never disturbing you or making you paranoid as you browse the web. You can disable alerts by loading up the Sygate main screen, going to Tools->Options, and in the "General" tab, tick "Hide Notification Messages".
Step 10a (Improving performance in Windows XP):
Okay, in this section we're going to try and improve the performance in XP with a series of tweaks.
Part 1 - Adjusting Visual Effects
Press the "Windows" and "Pause" keys simultaneously to bring up the System Properties window. Click on the "Advanced" tab and then on "Settings" under the "Performance" heading.
Now, I personally recommend unchecking everything EXCEPT for the following:
* Show shadows under menus
* Smooth edges of screen fonts
* Use visual styles on windows and buttons
. Click on "Apply" and then "Ok". Now before, you close the System Properties window, read on!
Next we're going to disable error reporting. You know that box you get asking if you'd like to send a message to Microsoft saying your program closed? Yeah, no one likes them so lets get rid of them. Click on the "Error Reporting" button at the bottom of the panel and select the ""Disable error reporting" radio button, and uncheck the box underneath it. Click "Ok".
Now click on the "Remote" tab and uncheck the checkbox to disable remote assistance.
Right, we're done with that section so you can click "Apply" and then "Ok"!
Rightyo, lets disable Hibernation as well to improve the performance further. Go to "Start" > "Settings" > "Control Panel" > "Power Options". Click on the "Hibernate" tab and uncheck the box.
There are a number of other tweaks you can do, but not all of them are preferable/user friendly! If you'd like any more tips, feel free to post/request/PM!
Step 10b (and finally...):
Finally, you want to de-fragment your hard-drive, after doing so much to it. First boot in to safe mode (see earlier steps for instructions/link to instructions) to ensure nothing except core Windows is running. Now within safe mode, head to My Computer, right click on your "C:" drive and choose "Properties". Click on the "Tools" tab and then "Defragment Now". Click "Defragment" and, if necessary, let it run overnight. Do not reboot the PC during a defragment - if you absolutely must stop it, click "stop" within the defragment window, wait for it to finish what it's doing, and only reboot when safe.
Note: If you have any problems defragmenting, eg it gets stuck for more than an hour on the same point (take note of the percentage, the stage, or the file it's on, and ensure it definitely does seem to be "stuck" - particularly if there's no hard-drive activity), then you may want to do a full "disk-fix" first, before the de-fragment, which can fix problems. Accessed from the same "Tools" menu as defragment, select "Check Now", select both "Automatically Fix File System Errors" and (here's the one that will slow this scan down a lot) "Scan for and attempt recovery of bad sectors". It may require you to reboot (and "schedule the scan") if you are doing this to your C: drive - do so and let it finish scanning entirely, before heading back to safe mode and trying the de-fragment again.
I know it is VERY long indeed, but this is more like a spring-cleanup for your computer.
Notice most steps you can actually skip, but if you follow and do everything in THIS guide, it will be running as fast as a new computer and the virus protection that i included is one of the best out there and it is also free too.