I've had this PC for a number of years without any significant problems. Just finished installing driver for matrox g550 graphics card and done a restart. It restarts fine and i change screen resolution to maximum in display settings 3 or for seconds later the damn thing switches off without a word of warning. Now when i press the power button i get 4 or 5 seconds of power, no booting up or anything happens, and then it switches itself off. Have tried unplugging everything but the power cable and the same thing still happens. Anyone have any ideas?