By the way, welcome to BC,
NealG, I just noticed you are a new member.
Your new video card needs an AGP slot so its not compatible with your motherboard, as they say.

What you need is a PCI video card that will fit one of your available slots. As this is fading technology the price of this type of card is becoming much cheaper as compared to AGP (also fading) and PCI-E (the emerging new standard).
Not knowing where you live I went to Newegg.com to find a couple of cards you could compare and that will work in your machine. I'm not recommending these cards as I have never had the particular brand I'm just illustrating what type of card to get. See the
XGI V3XT 64MB PCI and the
XGI V3XT 128MB PCI Volari's. Note that in their specs they both mention DirectX9 and that you can 128MBs for only five dollars more than a 64. Also note they are both
Retail rather than OEM. An OEM part is supplied without accessories as opposed to Retail that gets you accessories, in this case a driver CD and an S-Video cable.
Your current video setup is incorporated into the motherboard and uses 11MB of your installed ram so that will be freed up for your game. You will need to go into the bios and disable that on board video when installing a PCI card. This is not as difficult as it sounds.