I really want to upgrade my Nvidia Geforce fx5200 graphics card to an ATI RADEON 9600xt but I only have a 250w power supply...will this cause a problem... because i have seen many ATI RADEON cards needing a minimum of 300w

A new power supply is not expensive and is pretty easy to install. You might want to read a good report on power supply units over at Tom's Hardware to help you make your decision: http://www.tomshardware.com/howto/20050228/index.html.Here's another link to a tweak guide for the ATI graphic cards that I like. Page 2 is a discussion on power supplies....http://www.tweakguides.com/ATICAT_1.htmlJim

you need better psu. my old radeon didn't even work properly with 300w.