Intermittant resets

[maz29]

This is not a question about a new build, but an existing that I had working well, but am now having a problem that I just can't solve. Thus I was hoping someone in this forum might have an idea.

The symptom is that the system began resetting itself at seemingly random intervals (it ranges from about 1 hour to a half a day (it's not a software lockup, it acts just like someone pushed the reset button when you were in the middle of using it). The computer was stable until I went on vacation and came home to a dead power supply. I replaced it with an identical one (an Antec 380W TruPower) and it booted up just fine, but now has this annoying reset problem.

At first I figured the new power supply was unstable so I took it back to the store and replaced it another new one. The problem still persisted so then I figured maybe when the power supply got killed some other components were damaged. So far I have replaced the motherboard and swapped memory with another working computer but still observe the same problem.

I doubt I got two out of the box bad power supplies so I assue it is something else in the hardware. Any suggestions on how to further troubleshoot this would be greatly appreciated.

[newbuilder14]

Would you mind listing the specs of your build?

[maz29]

here they are (sorry about not including in the original post):

Antec 380W trupower PSU (mounted in an Antec Sonata case)
ASUS A7N8X Deluxe mobo
Athlon 2800+ XP CPU
ATI Radeon 9600 video card
2 512MB sticks of Kingston PC2700 RAM
1 80GB Maxtor HD (on IDE connection for the system drive)
1 250GB WD SATA HD (for additional storage - this is my media PC)
Sony DVD/ CD RW (I don't have the model umber handy)
XP pro

as I mentioned in my original post, the system was stable and workig well for more than a year and a half. I appreciate any suggestions anyone may have. This one is driving me kind of nuts.