Whenever I go "Start", "Shutdow", the computer reestarts insteads of shutting down and powering off. Is this likely to be a hardware problem or software? What are some possible causes?
its more than likely hardware. And in further detail, it is probably your power supply. If not your powersupply it could be a wiring problem.
possible fixes:
1) replace the power supply (dont do this first)
2) rewire your whole system (look at your mobo manual if you have to)
3) make sure that you are plugging all required power supply connecters to devices and make sure they are snug, not loose.
check the windows website, there is an issue where pc wouldnt shut down just reboot. Wife's computer did that and they had a patch for it. hope that helps