Viruses are just programs like anything else. They can be designed to do any number of things such as turn off the hard drive. I would suggest visiting this thread and following the steps one by one.
Ignore my last post. Happened again, kept PC on for ~40 min with no crashes. It could be a really odd coincidence but i've never had it happen with any game, only with browser games...
Disable all other plugins/extensions while playing. You can do this by typing "aboutlugins" in address bar.