HELP! If u know a lot about computers, plz help me! Mine's messing up...?

I have charter internet, which comes w/free spyware/virus protection. Something isn't right. My PC has started going VERY slow. Sometime Internet Explorer will shut down for no reason. Programs won't respond. I've done virus scans, no viruses found. I've done spyware scans %26 everytime I do one, it seems to find ''malware from ''clickspring'' in my windows/system32/N?lookup.exe folder. Everytime I reboot, I get a message that a virus was found ''trojan downloader'' in my win32.purityscan folder. Sometimes, while surfing the net, my charter virus/spyware protection icon gets an X over it %26 says there's a malfuction in it %26 I have to reboot before it works again. I've used disk cleanup, defrag, several virus %26 spyware scans. I've deleted programs (I keep getting the message that I'm running low on virtual memory as well). I have a lot of important things on this computer %26 can't afford to lose them (%26 cnt afford to pay 2 hv it looked @). What cld be wrong %26 how cld I try 2 fix it?

HELP! If u know a lot about computers, plz help me! Mine's messing up...?pop up blocker

If you try every option and have no luck, you may have to reinstall your operating system.

Use the disks that came with you computer to reload your operating system.

1.Make sure you can reload all programs you paid for. (ex: Photoshop)