Thanks for all your help guys. Ok, some updates.
I tried bumping it down to 333 and it didn't help.
Took out the 2 sticks of 3200 memory and put 1 stick of 2100 memory in. Reset BIOS to defaults. Didn't help.
Took out SATA drive , put in IDE, cleared CMOS, installed 2000, still keeps rebooting.
Put the SATA drive back in and put it on it's on power cable and the Video card on it's on cable. Didn't help.
Oh and i've replaced the mobo twice.
Some other info:
I am running this through a switchbox because i only have one monitor right now. Can't imagine that's the problem though. Also, when i first put this machine together, i installed Win XP Pro just fine and in fact the box worked for a few weeks. (with the BIOS at defaults and the exact same components i have now) It then started to rebooting itself once a day, then once an hour, then every few minutes, then i couldn't even get past POST. So i though i had a virus and reformatted the drive and have had this problem since. However, since i've replaced everything (except CPU and Video), i'm stumped. Plus, i don't understand why it worked for a few weeks without having to do anything to the BIOS.
*sigh*