My pc restarts everytime I watch a video after 5 minutes (e.g. on youtube or if I watch a video with the windows media player) . a) I've already done a memory test (the memtest ran for 6 hours and didn't show any errors) b) I formatted the hard drive and reinstalled windows XP. The pc still restarts. c) I've cleaned the interior of the pc from dust d) I monitored the temperature of the processor and it lies below 45°C. e) The pc does not restart if I play games. Any help is appreciated.