My PC is shutting down after few hours(?) without BSD, but keyboard lights, power LED, fans are running (it's not sleep mood or hibernating). To switch them off I have to switch off the UPS, holding the power button doesn't help. Then the system boots up normally like nothing happened. I checked all the cables and they seem to be fine. I haven't made any hardware or software changes recently.
System Information
OS: Windows 7 32-bit
CPU: Intel E5200 @2.5 dual core
RAM: 2GB Kingston
VGA: Nvidia GT240
MB: Foxconn G31-MXP
HDD: 1 x Samsung HD322HJ, 1 x Toshiba DT01ACA100