Does it do anything? If not, check power the best you can, don't rely on it worked before, prove it. You can even remove the cpu and see if it beeps in protest. If it doesn't do that and you know power is good, then recheck "everything", you can't take anything for granted, check on another system, one item at a time if possible.
I'm re-building my old computer from parts that I've upgraded. My problem is I cant get it to boot, even with a barebones set-up with just a stick of ram and video card, both of which worked on the motherboard. The power comes on and the cpu fan spins, but no beeps and the monitor remains black as if it's not going into the bios. I've removed the cmos battery and unplugged the motherboard and waited over 10 mins, (no cmos jumper)and still no change. Any suggestions would be appreciated.