Sounds like the virus is screwing with your system, doing stuff that would lead the CPU core to fry itself. The system is probably shutting down to protect the CPU. A friend of mine had a virus on his laptop that caused the videocard to overheat and now it is just screwed(thats what he said anyway).
Why not just wipe your 180GB drive clean and do a fresh reinstall with windows?
Also are you sure it is not a power supply problem, with things not hooked up right? A bad PSU can cause the system to shut down too.