Recently, one of the PC had no video. The fans were running. It had no beep code. The first thing I thought it was video card problem. It’s on board video card. I added a video card to it. Not helping, it still had no video. It’s power supply problem. Then I brought a power supply tester to test it. The power supply was fine. Then, it must be motherboard. I was lucky, I had a spare motherboard, I thought. After change the motherboard, I still got the same problem. I couldn’t think about what’s wrong with it. Search it from online. I had done all what were said on the web. No helping info was found. I decided to buy a POST testing card. Tested it with POST card, I found the problem. It was the memory.