Portal 2 crashing computer

[Meresgi]

So fiance just got Portal 2 on the steam summer sale, but each time she boots it up it crashes her computer completely and forces a reboot. Anyone had an issue like this? She's looked up and found other people with similar issues but there are no fixes or help that she can find so I figured I would try here.

[Sonomaa]

check video card drivers, thats usually the problem with those sorts of things
desktop or laptop, if its a laptop does it have optimus
nvidia, amd, or intel video card

[Mooshywooshy]

I had this issue, I had to update my mobo bios

[Meresgi]

Desktop and Nvidia GTS450. Drivers are up to date, i'll try the bios update.