What graphic card slot do i have

I'm thinking of buying a new Graph card but don't know which slot i have, how can i find out?

you should go for the GTX275 if your motherboard and PSU can handle that beast. If not go for the 9800GT or GTS250

Often times, if you open up the case, the type of slot will be printed right there next to it on the motherboard itself. If not, see if you can find your motherboard's model number and look up the specs online.

If you want a visual example:

In this picture, the PCI Express slot is the black one and regular PCI slots are white.

In this picture, the AGP slot is brown and the PCI slots are white.

In extremely simplified fashion, regular PCI is pretty short and starts near the edge of the board, PCI Express x16 is long and starts near the edge of the board, and AGP is long and is offset a couple inches from the edge of the board.

Basically, if you have an AGP slot, get a HD3850 if you have a big power supply, HD4670 if you have a small power supply. If you have a PCIe x16 slot, there are too many options to list but many good ones -- this is the best slot to have. If you have only regular PCI slots, throw away the motherboard.