If it is the model I am thinking of it is a mini tower format desktop. Very "budget" kit that came out around the last quarter of 2003.
Typically, it has a 2.5GHz Celeron and 128Mb of RAM.
I have only heard of performance issues, as it also has 32Mb shared video which doesn't leave enough to run Win XP smoothly.
If it is the MoBo then I don't honestly think that there is much you can do economically. You would have to get a Compaq one, as you don't have a full Windows XP CD............and Compaq parts are rather expensive.