Motherboard BIOS Beep codes

When I turn on my machine, nothing happens, no video and the PC speaker beeps short and continuously. I read on a forum that bios manufacturers have their own custom beep codes and that shot continuous beeps mean a power supply failure. I've gone and bought a new power supply and this didn't help. I also read somewhere else that it could be a CMOS battery, video card or memory problem. I have replaced the battery, removed the video card and removed the memory one chip/card at a time to eliminate the cause but the pc speaker still beeps. Any idea what this could be?