Old computer: HELP!!

I was having trouble with my sisters computer. It would not boot sometimes. When It would boot into windows it worked fine. Allthough when I chose to restart the computer it would just turn off with no reboot. When it was off I would try to restart it, an once out of every 20 times it would boot an run normal other than using restart. It was a Gateway computer with AMD athlon 64 X2. Also when I tried to start it and it wouldnt boot the fan hard drive (ect.) would come on. My question is that a processor problem? The motherboard was replaced with one from ebay. When I checked the board it had a bent pin touching another pin on the IDE cable conecter. I want to strip the processor, memory, harddrive, an use it ont a new motherboard from newegg. I just dont want to wast the money on new parts if the processor is bad. I beleive it was the motherboard but im not shure.