|Don't hit the panic button yet & do NOT reinstall the OS...that should be a last resort.|
Start by installing CCleaner-Slim. 1st run the cleaner, then scan for registry errors...remove everything they find. Then click on Tools > Startup & see what's listed. There should be very few entries...the only things required are sound, antivirus, antispy, firewall & network connection. There's no need for stuff like Quicktime, RealPlayer, iTunes, camera/scanner/printer software, messenger programs (Yahoo, AIM, etc), MS Office, Adobe, Java, etc or any other programs to load until you're ready to use them. All they're doing is sucking up valuable resources. The same can be said for most toolbars...Yahoo, Google, etc. They all suck the life out of the system plus they're all forms of spyware (if you don't believe it, try reading their privacy policies). And you should be doing all cleaning & scans from safe mode with the internet connection temporarily disconnected.