Dimension E510 Continuously Reboots

This problem is on a Dimension E510 with BIOS version A00 and Windows XP Service Pack 2.

A few weeks ago, my son complained that his computer wasn't working. I checked it out and it wouldn't boot into Windows. The computer would power up OK, but whenever it tried to start Windows, the computer would reboot and start again. I tried Safe Mode and Safe Mode with Command Prompt and the behavior was the same.

I removed the hard drive to save any files I needed and proceed to restore the hard drive to it's original state by using Ctrl-F11. This completed successfully, but the same continous reboot behavior persisted. I did this a second time, but still no difference.

I ran all of the diagnostics on the utility partition several times and there were no errors reported. I also ran the hard drive diagnostics, also with no errors reported.

Finally, I opened up the computer and removed and reseated the memory modules and all connectors. I also reset the CMOS settings. Still no luck.

At this point, I don't know what else to try. I'm suspecting a hardware problem, but without any errors reported, I don't know what it could be.

Has anyone else encountered something similar? Is there something else I should try before tossing this thing in the scrap heap?

Steve