I have a 500W ATX PSU with a P4 630 Processor and Gigabyte 945G Pro motherboard. I also have a SATA hard drive. When I turn on my computer for the first time, after several minutes, my computer shuts down and then restarts. After this, it works normally. This happens every day. I have run memory diagnostics and my RAM is working normally. My CPU Fan and all chasis fans are also working, so I know that overheating is not the problem. I also have updated to the latest BIOS just to be sure. The only thing left that may be causing this is the PSU. My question is can the PSU cause these intermittent shutdowns?, or is there something else I have overlooked? Thanks.