Well, that is seriously underpowered equipment for Windows 7, but the demands of that game are modest for such a recent release.
Your system specifications are here:
and the game minimum requirements:
The key factor seems to be:
"32 MB DirectX 9.0 compatible video card"
You'd need to upgrade to an AGP 4x video card with at least 32MB of RAM, DX9 and Windows 7 compatibility and modest power consumption as your system only has a 235W PSU. The standard Vanta supplied is a low profile card, but has a full height backing plate, so I don't think a low profile card is essential. I'm out of touch with the market for older AGP cards, but maybe if you could find something like a 128MB nVidia 6600 at a market or on eBay, it might suit.
Other posters may have further suggestions too.
Edited by Platypus, 07 June 2011 - 08:27 AM.