Lost Ethernet Controller for my Dimension 4400

I lost my ethernet controller when I recently installed windows vista.

I have a dimension 4400 and recently installed windows vista on my computer. That is when I lost my ethernet controller. I don't know if there is a drive compatiable out there for my poor old computer, so I am thinking I would have to uninstall windows vista and reinstall windows XP. If there is something out there I can buy or download, then that would be great.