I was recently attempting to fix my fathers friends computer, and this is what I ran into:
It spontaneousely restarts in windows xp or 98, so I booted from CD-Rom to begin a re-install and while booting off of CD-ROM after XP had loaded drivers the PC restarted. So I checked the temperature and it was 55 Degrees Celcius(which is usually enough to crash AMD's) but it should not restart it. So I checked the voltages for the power supply and those were fine too. Then I thought it could be his DDR RAM, so I removed one stick of 256 and then the CD-Rom loaded perfectly and the install began. Soon after the install of the files, XP began to install devices, and at this point it restarted again and continued to do so for quite some time. Finally we finished the install of XP but the computer still restarts spontaneousely. So I thought that there might be an IRQ conflict, so I removed the sound card, ethernet card, turned off On-Board audio and disabled both serial Address's. Then I thought that it might be his HD so I removed his CD-ROM so that the only device in his computer was then his Video Card and his HD. After doing this the computer restarted continuously over and over every 12 seconds or so. So I put the CD-ROM back in and we were able to get into windows IF, and only IF, we skipped the ChkDsk that wanted to start before running XP... if we allowed it to run then it would restart the PC, if we skipped it we could get into windows. So I began thinking that it may be a bad FPU or something on the MB but that just wouldn't make sense cause during install there surely has got to be many mathematical errors if the FPU was messing up.. so I removed that from the possible list of errors. Now here comes the messed up part, his Boot.INI was corrupt so the OS, by default, tried C:\Windows. So I checked the Boot.INI and it was about 1/8th an execution, it went "MZ... This program cannot be run in dos mode ..... @#$%$##^ etc..." up to 1KB(which did not run, I tried executing it). So I deducted that the errors could not be the following:
Power Supply: Because restarts usually happend in the same places.
RAM: Because it was not having parity errors.
IRQ, or DMA conflicts: Because the computer did not halt.
So I have come to a final decision that if there were bad sectors in the HD then it would restart the computer whenever they were accessed, this would also be correct in the case of the boot.INI because that would've proved that the Format of C was unsuccessful(I guess format did not restart the pc because it writes, and does not verify) and that Boot.INI was written to a 'Bad-Sectors' on the HD(and I doubt windows install would mess up and write EXE's in placement of Boot.INI). So I am later going to remove his HD, back it up, and do a Low-Level Format with Maxtor's Diagnostics Utility.
The owner of the computer said that it all started one day when he was playing SpearHead(So I automatically thought Over-Heated CPU, which caused damage) but then he said that whenever Norton would scan a certain part of his HD it would warn that it could not Access the HD then the computer would restart shortly after.
Hes running a: AMD XP 1600+ and an ECS MB with 512 MB DDR RAM(I didnt record which model), and a 40 GB Maxtor, and a GeForce Ti4200
I was wondering if anyone has had any similar 'Freak-Problems' like this one. Also, thanks for reading this long and likely annoying message.