Ahh.. I remeber solving same problem a couple of months ago but couldn't find that thread now..
OK here is it again:-
1.) Download Latest Antivirus (Kaspersky-recommended)
2.)Install IT (It wont be a problem...)
3.) Turn Off System Restore Service by Going to System Properties/System Restore TAB.
4.) In Safe Mode.. Scan Your PC. Delete every infected file..(It can mess your system badly... so be prepared.)
5.) Boot in normal mode and scan again.
7.) I think problem will be solved, so come here and post that problem is solved.