This has never happened before. The computer is custom built and is a little over a year old now. Specs: 450w psu asus p4p 800-vm mobo p4 2.6 1gb ram radeon 9600 pro 80gb wd hd cd rw zip floppy ethernet (cable) Here's the situation: A few days ago I was getting error messages when I closed internet explorer saying "memory could not be 'read'". I pressed ok and everything still worked fine. Next day I restarted and there was only one error saying "memory could not be 'written'". Next day my friend comes over and was doing some work in excel when suddenly my computer turns off. Fans stop spinning, hard drive isn't spinning, no power. My monitor and speakers are still on. I am also using a back UPS. I'm sure it wasn't just a random power outage. Anyway, I try pressing the power button on the front of my machine. Nothing happens. I unplug everything, look inside to see if there was possible a short circuit. Everything looks (and smells) ok. I plug it back in and turn it on. The computer works. He starts up excel again. BAM. Computer turns itself off again. Again I try to press the power button, but it doesn't work. I turn the power off on the PSU. I switch it back on and press the power button and it works again. This happens a few more times on random occasions. This happens when playing music, surfing the web, playing games, typing documents, looking at pictures, anything I do. I managed to get a full virus scan one time before it restarted. No viruses were found. I also checked the temp of the mobo and cpu and it is never above 45c. Today I tried starting up the computer. It didnt turn on at all. Even if I unplug it and plug it back in, turn off the PSU, turn it back on. Nothing works. I think its a faulty PSU, but I want to get a second opinion. I am a little edgy about the memory read/write errors. But even with bad memory, the computer should at least power up, right? Thanks.