have power up, both CD drives light up and hard drive is fine (moved it to another PC- via external casing and formatted it and reinstalled XP fine) but no video on tower, there are three video cards one came with the barebones and the other tow are ATA cards and hooking up monitor to each one... nothing.

It is hard for us to tell if you have a bad motherboard if we have no idea what your motherboard is. Could you also supply some info about the RAM, cpu, PSU ? Are you saying that you tried 3 different video cards separately ? What type of video cards are the other two, PCI, PCI-E, AGP ?

sorry, and I do appreciate the help. It is a barebones system that was built approx 6 yrs ago.. the MB is a MoBoStar P4-VIA series one video card was already onboard, the other was as well, so I do not have too much information on those the one that was installed after was an ATA card 36MB, the last two installed in PCI slots on the board. It is running a Intel Celeron D CPU 1.8 GHZ with 512 MB RAM DDR, I think 640 pin. the problem is that it was starting up running fine, then once in awhile there was no video activity on start up, the monitor would flash, then nothing, the PC was set up to run off the ATA card, so did the usual routine of taking the monitor testing it on another PC, monitor is fine, tried hooking up two monitors to dead system on the different video cards, nothing.. you can hear all the drives ( 1 HDD 2 optical) start up and cycle through fine... just no video or sound ( PCI slot Creative Sound Blaster)..

I'm a little confused about your video card setup. I would just have one video card installed and see if you have the same problem. Do you have drivers for the onboard video and both video cards installed at the same time ? It also might not be the video cards at all-what are the specs on your psu ? I would also download and run memtest to test the ram. When was the last time you blew dust out of the case and from the cpu fan ? Use a can of compressed air to blow some dust out. You may also have to remove the heatsink & fan, clean off the old thermal paste, and reapply new thermal paste.