not sure whether to put this here or video card forum, but will my 250W power supply be able to run a 2.8 G p4 and a 9800 pro? if not, how much W do io need? (it currently powers a 1.8 p4, ti4200)

I would say no, just because you wouldnt want that small of a PSU to start with in any PC, I would definitly get a new PSU, maybe about a 450W to be on the safe side, mine right now is a 600W and I'm thinking about getting another

I highly doubt that 250watt PSU could power a 2.8 p4 and a 9800pro. I would recommend at least a 400+ watt quality PSU. Let us know what the maximum amount of money you would like to spend on a new PSU and we can give you some recommendations.