windows XP keeps rebooting

Win XP keeps restarting, sometimes before it loads and other times after the desktop appears. The computer has a biostar p4m800-m7a motherboard with 2.93ghz p4 processor and 2 gigs of ram. I can start in safe mode and I have turned off the auto restart but it still reboots. Sometimes it will boot up but only about 1 out of 8. I do not have the windows disk for the computer but I do have an xp disk. I have Avast anti-virus, and Malwarebytes and have updated and ran both, and have also run Advanced System Care and Ccleaner. Any help would be appreciated, Thanks

 

Greetings, nvsbldd1...

To verify: does your computer spontaneously reboot while Windows is in Safe Mode? If not, then some startup program(s) and/or driver(s) must be causing the problem. There are better ways of managing startup programs, but for troubleshooting purposes you can run msconfig and disable all entries listed in the 'Startup' tab, then selectively re-enable items on the list to identify the culprit(s).

Also, please clarify the following:

 

to clarify the windows xp disk I have is not the one used to install on this computer. And windows will operate in safe mode without rebooting.

 

Understood - thank you.

Then please try the aforementioned edit in the msconfig Startup list to try to ascertain the problematic entries.

 

I started windows in safe mode then disabled all startup programs but the system still reboots, Any ideas?

Thanks