To best answer your post you will need to post your current computer information.
But here are generally what you need, in my opinion, to upgrade from that antique GPU Card to a supported GPU Card.
1) What is your budget for buying a GPU Card
2) What are you planning on using it for, Gaming, Rendering, Video editing, just normal browsing, etc.
3) After selecting your GPU card that you want, see if your PSU is powerful enough to support the GPU Card/CPU and your PC. Plus your current PSU has the proper PCIe Power cables to connect to the GPU Card , if applicable
4) Make sure your Motherboard will support the new GPU Card
5) Make sure you have room in your Computer Case since most GPU cards take up 1 to 2 PCIe lanes in width and are quite large in size.
