Can you help me? It seems my computer is infested with worms like: email-worm.win32.brontok.q.

How can this be cleaned up?
In addition, my computer has been giving me problems when I try to download all kinds of programs. When the computer begins the download, it suddenly says "Windows is shutting down" - and the computer turns off! This has happened when I tried to download anti-virus programs and other programs.
Once I was able to download Firefox. And it was working. But the version I downloaded was not in English. So I removed it. But whenever I try to download it in English, the computer turns off! Could this problem be related to a worm or a virus?
Any suggestions? Thank you. Thank you!