The pc is a Compaq 5000US with a 750 AMD Duron processor and Windows XP Professional loaded. It has a 30 GigHD, 384 MB of SDRAM and the standard Compaq sound and video cards. At any time(within seconds of starting or after 5 to 6 hours) the pc locks up (no mouse or keyboard movement and the system task bar clock freezes along with the video image). Rebooting the pc usually doesn't work until the next day or so provided the sucessive attempts to reboot following the event lead to no monitor feed and a boot up to the desktop. As part of these "events", the pc usually performs a checking of the various drives (CD, CDR, floppy and HD)but doesn't end up starting up fully using the HD's startup steps. These same symptoms occurred with Windows ME on the pc. I've installed a new hard drive with a clean install of WinXP Prof., tried various RAM chip sizes and pairings (all at 64 or 128 PC 100s SDRAMs), software testing (before it locks up)yet the problems remain. Could the video card, the motherboard HD controller or the power supply be bad? I doubt that there is a software problem and am running out of easy things to try for testing the stability of the pc. Sometimes rebooting works but then it may not run cleanly for long. Most of the times it doesn't reboot at all after locking up. Are there any "easy" things to look for that won't cost a lot of $, if not free?

I have the same problem - PC freezes with no error message or apparent cause. I can re-boot it and it works instantly again but there is no pattern to the crashing. Sometimes after 3 or 4 mins or sometimes after a few hours. I've already had the power supply replaced but that didn't make a difference. System Emachines 866MHz PIII 256MB, 30GB HD 64Mb Hercules Prophet Graphics (used to have intel 810 but was crashing then as well) Windows Me