Ok here is what to do:
Download a Free copy of Avast home here - http://www.avast.com/free-antivirus-download
Install it, once you have done this it will as you if you want to run a check on bootup, select yes.
Upon boot up tell it to move detected files to chest (once prompted).
If this does not clear your issue try some more programs:
Spybot S+D here - http://download.cnet.com/Spybot-Search-amp-Destroy/3000-8022_4-10122137.html?tag=mncol
Malware bytes here - http://www.malwarebytes.org/
If your running xp remember to turn OFF system restore as many viruses can hide here, which antivirus programs do not always search. Once your computer is clean remember to turn this back on.
Still having trouble, keep pressing F8 while your system is booting up and load windows in safe mode, then run these programs again. If you have a nasty safe mode will not allow it to start up in safe mode as a service or process unless you tell it to.
If all else fails take it to a computer shop to have it fixed. REMEMBER TO TAKE BACKS OF YOUR FILES BEFORE YOU DO ANYTING.
Good luck.