Here are the 3 completely FREE scanners we use- they have no strings attached.  Just don’t click on anything to buy- they do try to sell the full version:

http://www.malwarebytes.org/ 
Click download, then download & install- run full scan.

http://security.symantec.com/sscv6/WelcomePage.asp 
Click Continue to Symantec Security Check, then Virus Detection- keep giving permission to the scanner on the yellow bar at the top of your browser- you may have to refresh or click the button again to get it to work.

http://housecall.trendmicro.com/ 
Click Download HouseCall (32-bit most likely) then click Get HouseCall Now.

Between all those scanners, it should get rid of any viruses.  If your scans pop up more than 5 Trojans, it's safest to format and re-install Windows, to be absolutley certian you have gotten rid of the virus.  Be sure to backup your documents and files first.

Important note: After you have re-installed, be sure to change all your passwords- your computer was comprimised and you should treat the situation as though you know for sure someone else now has your password to you online bank, Facebook, etc.  because, there is a very good chance, somone does.