1. I removed the heatsink from the processor to clean dust out of the fan. When reinstalling it onto the motherboard I broke one of the clips that goes through the hole in the motherboard. The heatsink is pretty tight and 1 side of the clip is still attached and in the hole. I did not apply more thermal paste or remove the old dried up paste but I have some in the mail. I do not think this is the problem (but I am far from an expert) since the computer shuts down before the processor has time to get too hot.
2. I bent a capacitor but to no more than 80 degrees (where it was originally 90 degrees to the mobo) and straightened it back out.
3. I did not protect against static transferring from my body to the mobo during the process. When I reinstalled the heatsink the board flexed a bit so I think I may have messed the board up.
4. I have had problems with an overheating CPU when running memory intensive programs but I installed more fans and the problem seemed to be solved.
I'm thinking the motherboard is the culprit since I was not careful when doing the switch. I'm not really sure though. The processor could be the issue since I messed with the heatsink but the fan is working perfectly. Could the heatsink being a little loose be the problem? It only moves an 1/8 inch at the most back and forth when testing its fit. The power supply is my other suspicion but I do not have a volt meter to test it. I do have another power supply but it has a 20 pin connector instead of the 24 pin required for my motherboard. Can I use this power supply to test the system or is that pointless? If I switch the PSU to 115 volt the computer will run without shutting down but will not boot up the HDD or anything else and no BIOS post comes up.
My system is:
ASUS P5VDC-X mobo
Intel Pentium D 2.8 Ghz processor
Western Digital 160gb SATA HDD
2- 1gb sticks DDR2 667 Kingston valuRAM
ATI Raedon X1300 GPU
Ultra 650W PSU- not sure of the model right now but it cost around $100 2 years ago if that helps