I had a PentiumD 820 2.8GHz processor with Gigabyte board and 1GB ram, and an AGP graphics card. I met up with a series of problems with this system.
First the graphics card didn't work. When I opened the cabin and checked, a capacitor in the graphics board had bursted. So I replaced with a local computer mechanic. Then it worked fine. Then after some months, same problem happend and another capacitor had bursted. I've changed that also. Then it worked for sometime and went of again. But this time no sign of hardware damage. So I removed the graphics card and used the system without it.
After a while I had a series of system restarts. Then it became very frequent. Sometimes, while booting even before seeing the winXp loading screen it will restart. I checked the motherboard with a computer mechanic. He said that some cpu socket pins were bent. Then he repaired it and it worked for sometime. Then same problem came. Now I checked the thermal seal btw the cpu and the cooler. it was very thin, I changed it and it worked for sometime. Then same problem happened.
Now I thought there is something wrong with the motherboard and changed it to new Asus motherboard. For this motherboard I put a XFX ATI Radeon 5450 graphics card. It worked nice for one day, then it also suffered the same problem. I checked the cpu temperature. It was too high. I thought the cooling is not proper and bought a costly thermal flux and applied it. It worked for one day. Then same issue. Now I suspecting the SMPS. Its rating is 400w. When I checked XFX website, they mentioned a minimum of 400w power supply.
So I thought of reducing the power consumption, so that it won't trigger the SMPS to restart the motherboard. So I removed the graphics card and checked. But no luck. its not starting up. I had 2 OS. WinXP SP3 and Ubuntu 10.04 64bit. Both the os are restarting after few seconds of loading.
I'm planning to replace the power supply and check tomorrow. But I'm not sure it that will work. And I'm not sure about the rating also. Please provide some expertise on what step can I take next.