Firstly, antivirus programs will NOT remove these as they are malicious codecs, although they may find reference to them and remove it but upon rebooting it's back again.
The following free tools have worked successfully in hundreds of removals of these parasites:
Malwarebytes Anti-Malware:
http://www.download.com/Malwarebytes-Anti-Malware/3000-8022_4-10804572.html?hhTest=1.
Download, install, update and select Full Scan.
Remove all infections that it finds after scan.
Spybot S&D:
http://www.safer-networking.org/en/download/index.html
Download, install, update and Immunize, then click 'Check for problems' then when complete select all and then 'Fix Checked'
Spyware Doctor Free Basic Edition - Realtime monitoring:
http://pack.google.com/intl/en/pack_installer_new.html?hl=en&gl=us&ciNum=12
Its free with Google pack, untick all boxes except Spyware Doctor. Download install, update and run.
SUPERAntiSpyware Free Edition:
http://www.download.com/SUPERAntiSpyware-Free-Edition/3000-8022_4-10523889.html
Download, install, check for updates, then select Scan your Computer, select your drive and select Perform Complete Scan
VundoFix:
http://www.symantec.com/content/en/us/global/removal_tool/threat_writeups/FixVundo.exe
Disconnect your computer from the internet
Run vundo
Restart your computer
Run the tool again to ensure no traces are left.
If there are the reboot into Safe Mode and run FixVundo again.
If your desktop has changed or icons are missing also use:
Wallpaper Hijacker Removal Tool:
http://www.majorgeeks.com/Wallpaper_Hijack_Remover_d4816.html
Note: You should hit all "Repair" buttons even though it may not say "Found!" This will fix a wallpaper hijack everytime if all repair buttons are pressed.
SmitFraud Removal
This tool will remove Desktop hijacking malware. Firstly, download the removal tool from here:
http://downloads.securitycadets.com/SmitfraudFix.exe
How to use:
http://cotojo.wordpress.com/2007/08/24
If the problem persists, turn OFF System Restore and scan with the above programs in Safe Mode, Right click My computer > select Properties > System Restore Tab > Tick Turn Off System restore on all drives.
After scans are complete and machine is clean remember to turn system restore back ON and create a new restore point.
EDIT: @Loou O...again you are posting links to a known malicious site: Spyware Cleaner 2008 creates the very same problems that many of us are trying to clean up!
You may have changed your username but still the same pattern...duly reported for Abuse of the CG.
@johan - Your answer redirects to Spyhunter, a known dangerous site which is used for phishing and scams.
http://www.mywot.com/en/scorecard/www.pcthreat.com
When will you people learn to answer the question WITHOUT directing the asker to your own site which violates the CG or to sites that contain even more dangers!