Ok, this is my motherboard: GA-945PL-DS3 (rev. 2.0).
When I bought this PC it came with Intel Pentium 4 3.0 GHz. Now, I bought new processor Intel Core 2 Duo E6700 2 x 2.66 GHz. I removed old CPU and I placed new CPU and nothing happened. I heard few beeps but system failed to boot. When I put back old CPU again (Pentium 4), system failed to boot again. No beeps, no BIOS, only black screen. Fan works and power is on but system fails to start. Can someone tell me what is happening? Thanks in advance.