BIG VIRUS TRIED EVERYTHING HELP!!!!!!!!!!!!?

first off, i tried to download some drivers for my nvidia motherboard but they turned out to be a nasty virus. every time i turn my cpu on it says "shutting down in 60 secs by nt authority\service". keep having to use cmd to abort shutdown. taskbar-gone icons on desktop -gone...wont let me restore. even happens in safe mode. takes like 5 min to boot (normally took 30 sec). tried symantec "w32.blaster.worm fix" as well as "fxser" fix both by symantec and both found nothing. scanned with avg found nothing. hav another melware scanner but it corrupted it. tried to reload original drivers from original cd but it blocked the setup files. im desperate and i need help.