Internet Explorer 8, Firefox, and Opera have perfectly good built in pop-up blockers. They must be enabled to work. After they are enabled pop-ups should be rare.
IE8 : Tools > pop up blocker > turn on
Firefox: Tools > options > content >Check "block pop up windows
Opera: Tools > Quick Preferences > Block unwanted pop-ups
If you get more than 3 pop ups per day with the browser pop up blocker enabled, you are infected with malware.
Scan your computer to remove it. I recommend
Malwarebytes' Anti-Malware (free)
SUPERAntiSpyware Free Edition
You must have active virus and spyware protection. You must also have a firewall.
Active Virus Protection: Install Free Avira or Free Avast. Avira is rated slightly better than Avast. Do not install both. Two active anti-virus programs they will cause conflicts when running.
http://www.free-av.com/
http://www.avast.com/eng/download-avast-home.html
Active Spyware Protection: Install Microsoft Windows Defender (free, Included with Vista). You can have more than one active spyware protection program installed.
http://www.microsoft.com/windows/products/winfamily/defender/default.mspx
Make sure your firewall is active. Windows firewall is fine, though there are more advanced firewalls available, each with its own pluses and minuses.
Also install to further harden your computer against attacks (require manually updating weekly), Install
"SpywareBlaster" (free) Blocks 12,749 items
"Spybot - Search & Destroy" (free) (Disable tea timer and SD Helper):
Mode > Advanced > Tools > Resident > Uncheck tea timer and SD Helper After each update click Immunize button > click Immunize
Immunize blocks 116,523 items
Spybot - Search & Destroy has a relatively weak spyware scan.which I rarely use.
Google names in " " below and click on first result.
To reduce you chances of being infected by visiting bad web pages and downloading bad software install
"McAfee SiteAdvisor" (free)
http://www.siteadvisor.com/
It places a box in your browser (Firefox and IE) that is green for safe sites, yellow or orange for questionable sites, and red for dangerous sites. When you want to download software go to the software manufactures web site and press the McAfee button and read the reviews sometimes even though McAfee rates it green reviews rate it red.
Install and at least once a month update and run:
"Malwarebytes Anti-Malware" (free version)
"SUPERAntiSpyware Free Edition"
Other good tools to install
"CCleaner" - free- cleans garbage from your hard drive
"Comodo Registry Cleaner 1.0.17.23" - free
"Secunia Personal Software Inspector (PSI)" - free -Checks for outdated, unpatched programs that are a security threat and shows patches if available.
"Belarc Advisor" - free- Lists all installed programs, many product keys, and checks that all Microsoft updates have been installed. It also analyzes your security level.
Good free online scanners; Run a different one each month or so. Rotate through the list.
"BitDefender Free Online Virus Scan"
"ESET Online Scanner"
"Kaspersky Lab Free Virus Scan"
"McAfee FreeScan"
"Panda ActiveScan"
"Symantec Security Check"
"Trend Micro HouseCall"
"Windows Live OneCare Safety Scanner"