The best way to find out what kind of video connectors you have is to open up your case and look at your mother board.
If it looks like this, the best you can do is PCI -e x1 as photon says.
http://support.dell.com/support/edoc....htm#wp1052309
If it is, you can order a card from here but these can be expensive as they are kind of rare.
http://www.ncix.com/search/?categoryid=2-108&q=PCI-e+x1