System BSODs when booting from HDD or UBCD4WIN

I am working on a Dell Dimension E521 system for a friend of mine. When booting, the system starts loading Vista, says it was shut down incorrectly and offers two options, start normally or startup repair. Both choices cause the system to reboot.

Tried rebooting with UBCD4WIN and it reaches a certain point, and reboots PC with no errors or warnings.

Rebooted and pressed F12, selected "Boot to diagnostic partition" and ran memory test. Multiple passes and everything passed. Ran "Custom Hardware" test and selected all available hardware components, all tests pass.

Now it gets tricky, when I tell the Dell Diag utility to test using the "Sympton Tree" method, tests run and pass successfully until it gets to "System Memory - MATS" and about 10-15% through this test, the system just restarts again.

First thought was hard drive corruption since diag partition is on HDD, ran MULTIPLE tests on HDD including HDD Manufacturer HDD diag utility, SMART detection utility and all tests passed. Hooked drive to another PC and ran chkdsk. Located a couple of errors on drive but they were repaired. Put HDD back in e521 system, still rebooting.

Replaced RAM module (system only came with a single 512MB module. Replaced with a 1GB module) and all symptoms were still identical. Removed HDD from system and tried to boot to Windows Rescue CD, starts loading and reboots system.

Then tried replacing Mobo and symptoms still persist.

Does anyone have any other suggestions on what I can check on this system? I am thinking with a 60GB hard drive and only 512MB of ram, my friend might be better to just buy a new PC anyway but I told him I would do my best to try and get it fixed, so ANY help or suggestions are greatly appreciated.

Thanks in advance.

 

Could be PSU but I would expect them to be a bit more random if it was PSU.

You could try doing a bare boot with just MB, RAM, CPU, GPU and PSU out side of the case on a piece of card. Could be something on your case shorting out but again, I doubt it.