PC won't turn off

[ghetto guy]

When I go to turn off my computer it goes through the whole shutdown process but it doesn't shut off. The power supply will keep running for a long time even after all the case lights are off and the hard drive has stopped spinning (with the old one I could hear it spin down, the new one is much quieter). With my old video card it would even display "Windows is shutting down" for a long time until I turned it off by hand (after I heard the hard drive spin down). If I try to put it in standby or restart it, it does the same thing.
My computer is made from a bunch of stuff from my shed and a motherboard my friend's dad gave me. The motherboard is an ECS PT800ce-a running the latest BIOS. The power supply is from my old computer and my step-dad had it in his computer before that.
Any ideas?

[Hootmon]

Sounds like your PS isnt getting the message from the mobo that its shut down.

Either you didnt plug something in right, or either the mobo or the PS are incompatible with power-saving functionality.

[JSZ]

I had this problem once. This won't help you but here's what happened.

I learned to live with it.

One day I decided I would like a faster CD burner. My son said that he had a spare so we installed that. Turns out it was an ordinary CD-ROM drive. I took that back out and reinstalled the old slow burner. Once Windows finished finding and installing the driver for the old burner the shutdown function started working again!

One of those things that make you go "Huh?!"

[ghetto guy]

Yeah, I've lived with it for a while. I just turn off the switch on the power supply. I'll have to see if I can dig up another one that will work.