Random freezing problem

[yokel]

Okay, i've got a really odd freezing/crashing problem going on with my workstation. It will run fine for hrs/days & all of a sudden freeze up & the processor light starts cranking. Sometimes it will completely crash & when it reboots the bios are unable to detect the drive that the OS is on. I'm able to fix this by simply turning it off, then unplugging the power cable connected to the OS drive & plug it back in. Then the bios are able to see it again & i'm able to set it back to the boot drive & everything loads fine. I haven't added any new hardware or software. I've flattened & reloaded the OS(XP & 2k), so i don't think it's OS related. I've also tested the drive with Western digitals data lifegaurd tools. Everything reports okay on the drive. I've also swapped out the RAM & got the same results. This leads me to believe that it's probably a power supply related problem, but wanted to consult others that have more experience than i. I also don't have a multimeter to test it. So, thanks to anyone who is kind enough to reply with their thoughts. k.

edit: Wanted to add that nothing seems to be overheating. All the drives as well as the power supply are fairly cool to the touch.



System info: Built approx. 2 years ago
Processor: P4 2.6ghz
MOBO: Intel PERL865
RAM: Geil dual channel 512mb ddr3300 x 2
Optical drive: Plextor 708a
hard drive: WD160jb 2 partitions: 40gb(OS) & 120gb(working drive), WD120jb(x2), WD120jd(sata)
Vid card: Ati radeon 9800
Aud card: Egosystems waveterminal 192L
power supply: Antec 400w
fans: 3x 5400rpm (1in, 2out) + power supply(2x) & cpu fans