well, you can use 9800GT on any motherboard, as long as the board has PCI-E slot on it...
Only dual core, right? so, if you can, OC it a little bit to 3.0GHz or higher then you'll good.
Also, add another 1GB of RAM, so the setup will be (1+1)GB = 2 sticks.
If the dual core is at 2.0-2.4GHz, he may not be able to set it as high as 3.0GHz, even more so if it's a prebuilt.
Can you tell us what psu you have? You need a psu with a 6pin cable, and a pci-e slot, also at least 350+watts.