Is it possible for a power supply to cause a lockup at any given time?  I replaced the motherboard and cpu, also thought maybe the harddrive was the problem so it was replaced but still it locks up at different times.  Sometimes it will do it while in BIOS setup, sometimes after a reboot with scandisk running, sometimes after a boot and sitting idle.  The only thing that hasn't been changed since this started is the power supply, case, and DDR memory.  Im running out of parts to swap.  Any help is appreciated.More info maybe helpful......like ram ......are they a match pair.?......operating system is?.....the more info the better to help you solve your problem...okIf the fault lies with the PSU, it would most likely shut down or reboot. Not crash.

You may wish to test the RAM by using Windows Memory Diagnostic as faulty RAM may cause the system to crash.check all your fans are working and clean I had a pc last week the cpu fan had a CARPET on it and had STOPED working all TOGETHER, the pc would run for about 30 mins the flock up,
another pc was in a cupboard with no air HOLES for air to move