What antivirus are you currently using?
I recommend AVG. If you do not have it or any antivirus at all, go to the link below and download it. After download, install and update AVG then do a FULL system scan of the PC. Hopefully this will pickup the virus causing you problems.
http://www.softpedia.com/get/Antivir...-Edition.shtml
If the registry is corrupted, try the link below to correct it.
http://www.bestshareware.net/registry-first-aid.htm
Any problems let me know.
Cheers