Computer virus infestations

A few weeks ago, my PC was infested by two different computer viruses about one week apart. I am not sure if both were present at the same time. One virus blocked all outgoing network traffic to prevent the downloading of virus scanners (I got around that by sending a scanner to it), the other one corrupted every windows executable file on my all of drives. The only thing that wasn't affected was the game Guild Wars, because the auto-update system overwrote its own executable with a new version. That virus was W32/Tenga.A