Froze up/Now Won't Boot-Up. Help!!

[t_bone47957]

My computer was working fine. Then the mouse quit working. Then the keyboard. So I rebooted. Now it does nothing. It flashes the mouse once and the 2 cd drives then the mouse or keyboard won't work. The monitor has no display. It has the inactive "yellow" light on the monitor. I took the hard drive out and put in another cpu. Works fine. I hooked monitor to another cpu. Also fine. I removed battery and tried resetting cmos. Then I thought it might be battery so I switched with a another battery I knew was good. Still nothing. Fans are running and hard drive is spinning. Also..floppy disk not loading.
I have a Compaq S6020. It is about 3 years old.

I have two hard drives (80 gig and 20 gig) the 20 is partitioned for windows and storage.

I have 500 mb ram.

2.5 processor.

No additional video card except onboard video.

The only additional cards I have installed is a video capture card.
I am running Xp.

Any help would be appreciated. I hope this is enough info. First time posting.

[JackWats]

Check your power supply and memory. If you can test the memory in another system, that'd help narrow it down a bit.