Removing Persistant Viruses

[Crazed Rabbit]

So my parent's computer has become severely infected after my brother disabled virus protection like AntiVir and Ad-Aware, in an effort to speed the several years old computer up.

Now, you can't go anywhere on the internet but virus sites, applications like task manager won't run, etc.

I installed spybot S&D on a flash drive and attempted to run it, but I got an error saying the .exe was infected and wouldn't run. I suspect this is the work of the virus (no **** Sherlock, huh?).

Anyways, I need some way to wipe a computer that can get past that executable block.

Any possibilities?

Thanks,
CR