its a standard PCI-e slot so theres no reason why it wont. its also a low voltage card you can run with a 300 watt Power Supply. I had it running with my Nspire 305 watt PSU with no issues with my settings at 2048, of course i was running a quad core pressesor too , your bottle neck i think with running that card is your cpu a single core 3.2 w/HT prescott based CPU.
http://www.newegg.com/Product/Product.aspx?Item=N82E16814121354 is the card
having read some forums on upgrading the CPU upgrade is limited to single core Pentium 4 prescott based 5x0 and 6x0 series Pentium 4 775 chips. while a better video card may help the video. i am not sure your cpu will work with you. maybe someone here that runs simular cpu can give some performance specs before you think about putting any money into the machine.
Note: 5X1 and 6XX series support 64-bit and the 6XX have 2M cache
i looked on ebay and they have 661 3.6ghz P4's for around 30.00
also i ironically have a 8400 here in the shop a customer brought in and i am not a big fan of the passive heat sink with the fan cowl over it.
also double check the caps on the motherboard they are commonly blown or bulging which if you have any makes this all a mute point