Your current setup, being many years old now, wouldn't support a good graphics card
I'd recommend saving up and buying a whole new system. You can build a decent rig for around $500, which would be over 9000 times better than your current computer. Definately worth it, especially if you wanted a graphics card for gaming.
"As a result of all this hardship, dirt, thirst, and wombats, you would expect Australians to be a sour lot. Instead, they are genial, jolly, cheerful, and always willing to share a kind word with a stranger, unless they are an American." -- Douglas Adams