I'd hate to see you lose everything when you don't need to...so you might as well try a few antivirus, anti spyware/malware programs before you reinstall everything.
You may want to try this...
First, do a disk defrag. Start, programs, accessories, system tools, disk defragmenter.
After that, go to www.download.com.
Do a search for Ad-Aware Personal Edition.
Download it.
Do a search for Spybot Search and Destroy
Download it.
Go here:
http://www.avg-antivirus.de/FreeAvgAntivirus/en_index.htmlDownload AVG Free Edition.
Then go here (probably the most important in your case):
http://www.emsisoft.com/en/Download aSquared Personal Edition (free also)
Go through the necessary steps and install all four programs.
After installation, start them up one at a time...go through the menus to look for online updates. Update each program for the latest virus threats. Make sure the updates have installed on each program, then reboot your computer into safe mode (probably by pressing F8 repeatedly)
After reboot into safe mode, do another disk defragment. Then run each program, one by one...on the "thorough" setting if available.
This will take a while.
Don't run two programs at once. If you do, they may conflict with each other and your system will slow to a crawl. Also, you may want to make sure they don't all start up automatically when you reboot the computer again. Look through the options menus and uncheck the "load at startup" option on each of them. This will prevent them from loading every time you start the computer, which can really slow you down.
After performing all of the scans on the most thorough settings, I suspect you will finally get rid of those darn viruses.
Good luck.