Okay, this is the weirdest problem I've ever hard with computers. Here's what happened: 1. I had a few years old Pentium D 2,8GHz processor running on Asus P5VDC-X mobo. PQI 566MHz DDR2 and GF 7600GS 256mb PCI-E, 350W power. 2. I updated the mobo to Asus P5L-MX to support faster PCI-E cards. Everything worked fine, despite the processor ran too hot (58C on high use) 3. Because of the overheating I replaced the thermal paste but it had no effect on the temperature. 4. I thought I used too much paste so I replaced the paste again. --- 5. Bang, no video when I turn on the computer. I tried taking off everything part by part but nothing worked. It didn't work even when I only had processor and used the integrated graphics port. Tried resetting the bios too. 6. Nothing worked so I put back the old P5VDC-X and it worked like charm. 7. I thought it was logical that the problem was caused because of the mobo so I bought a new one, Asrock G31M-S. 8. No video... Did the same steps to this one too. It also had integrated gfx but it didn't work either. 9. The old P5VDC-X still works. So I have no idea what's causing the problem. Is it the CPU? Mobo? PSU? RAM? I have no speaker on my case so I can't hear any beeps, but it won't start loading the OS from the hardrive and my USB mouse won't turn on. Tried using a differen't monitor too. The main point is why it stopped working suddenly on new mobo's but still works with the old P5VDC-X? Any ideas? Let me know if I forgot to mention something important.