I need help upgrading my video card. Suggestions?

Hello, Im currently trying to upgrade a computer that my friend no longer wants, its a nice computer, it just needs a new video card and a complete swipe of the hard drive. I don't know where to look or what to get as far as video cards are concerned. Im looking in the range of about $100-$250. I know that the old video card ( he took it out and connected it to his other one for he new computer ) was from NVIDIA.