This isn't a thread looking for a solution to a problem, I'm just trying to learn why this solution worked. My PC was freezing up frequently, and wouldn't get passed even formating the hard drive when trying to reinstall windows. I proceeding to testing the memory, the hard drive, and even unplugged all PCI and DVD devices, and just used an external dvd drive. Got a known good CPU from a friend and installed it and even ran a test on the power supply with a power supply tester and it told me it was good. I was pretty sure it was the motherboard, which I just recently replaced a couple months ago. Before I went through the hassle of sending in the mobo for a replacement I decided to try a new power supply and now my PC is working perfectly. I'm glad I got the PC working, but my technical curiosity has me wondering why it solved it. Both power supplies are 300w and have a 20 pin and 4 pin molex. And the power supply test told me the faulty one was working. I recently bought this PSU tester so if its not a good unit I might as well return it. Thanks to anyone who replies and gives me some insight into this issue.