An individual built the CPU, running windows XP, 256 memory. Its been up and running for about 1 year. When turning it on the BIOS did not see the hard drive. So I rebooted and went into the BIOS and tried to auto detect the hard drive. It found it, so I saved the configuration and system booted fine. After working for a while I shutdown the system for the day, next day tried booting and same thing occurred. So I went through the same steps as stated above; system came back up. Obviously, a problem and concern here; I couldnt stay to diagnose it at that time, but it was up and running and it was used all day. That afternoon, I went and bought a battery for it thinking that was the problem. After installing the battery and rebooting the system. Right in the middle of the reboot the power supply-dual fan started making a loud noise and the CPU totally died, dead. So of course, next I replaced the power supply-dual fan, thinking maybe it was overheating. After replacing that the fan unit on the motherboard started making a little bit of a noise so I thought what the heck I just replace the fan unit as well. After replacing all of the above everything seems to be working fine. But my question is how do make sure that it was the power supply and its not the motherboard itself. I do not have any fancy equipment like a voltmeter, storage oscilloscope or the PC Power Check. Is there any other way to tell without having just sit and wait or do you think that what I described above has fixed the initial problem? Any advice would be greatly appreciated.