I played Crysis on all of the "optimal" graphical settings for my Radeon HD 4850 (512 MB) and I got to the point in the game where you enter the frozen alien hive, after killing that North Korean general, and then my PC just shut off by itself. I'm not talking about a crash back to desktop, I'm talking about the power to the PC being turned off for no apparent reason. This happened to me a few times before, I played STALKER Clear Sky on "maximum" quality settings, and it shut off after about 25 minutes of playing. I'm running Crysis on 1024x768, 0x AA, Vsync, on all "high" (optimal) graphics settings. Could you please try to explain to me why I am having this problem? Has this ever happened to you? Every component on my computer is running on it's factory clock speeds. Including my GPU.