If you think your computer has been compromised by malware then please follow these instructions for proper cleanup.
Disable System Restore then reboot your pc, this will delete all old restore points. To do so for XP right click on your My Computer icon and select properties - system restore and then disable it. For Vista/7 right click on the Computer icon and select properties - system protection and you can disable it there.
Download and run
CCleaner, this will clean out all of your temporary and junk files.
Download, update and do a full scan with
Microsoft Security Essentials and remove all that it finds.
**FIRST UNINSTALL YOUR CURRENT ANTIVIRUS PROGRAM**
Download, update and do a full system scan with
SUPERAntiSpyware and remove all that it finds.
Download, update and do a full system scan with
Malwarebytes Anti-Malware and remove all that it finds.
Download, update and do a full system scan with
SpyBot Search & Destroy and remove all that it finds. DO NOT install the tea timer feature when installing SpyBot.
Download and run
AutoRuns and see if there is anything suspicious. You have to know what you are looking for but it is an invaluable tool, it is kind of like HijackThis on steroids.
Download and update
SpywareBlaster to help stay malware free.
Download and do a scan with
HijackThis 2.0.2 and post the results here in the forums so I can assist you.
Do ALL of the latest Windows Updates to ensure your OS is patched properly i.e. SP3 for XP and SP2 for Vista.
Download, install and run
Glary Utilities Slim and use the "1-Click Maintenance" option to cleanup and fix errors and problems with your pc.
Install
Threatfire it is behavior blocking tool that gives you an extra layer of protection along with MSE if needed.
If you need a firewall (Windows firewall is sufficient) I would HIGHLY recommend
PCTools Firewall, it's FREE, offers excellent protection and will not slow your connection down at all.
If you are badly infected I would suggest doing the scans in Safe Mode, to boot into safe mode tap your F8 key when your computer is booting. Also, certain infections may require a specific tool to target the specific malware you are infected with. 
