Yesterday my PC was working fine. Earlier today I installed a PCI wifi router card into my PC and replaced the RAM simultaneously but when I reassembled it and switched it on the monitor remained a blank screen displaying a "no signal detected" message. This happened several times. I tested the monitor on another PC and it was fine. When I switched it on again I listened carefully. PSU fan works, harddrive spins, CD-Drive spins still no signal just a pitch black. Switched the RAM back to combination which I know works. No response. Took out the PCI card. No response. Disconnected all drives. No response. Took out RAM and drives, no response. Noticed that there is no beep which occurs when I switch it on. What should I do? The warranty is over so is there anything I can try before replacing the motherboard? Any help would be greatly appreciated.