What's your budget?
There's only so much you can do with something that old. I did find a Pentium D 840 (the fastest CPU your board can run) here
It can only handle a max of 4GB or RAM, but 32-bit XP will only recognize 3.5GB (including video memory). You could go with 2 x 1GB
and either pull the 2 x 512MB or keep them in and make it 3GB.
You will need both a PSU and a graphics card. Here
is a decent PSU and here
is a good card.
All of these total up to $259. You have to decide if it is worth putting that kind of money into something that old.