So if I wanted to get a new grahpics card and this is my computer

HP Pavilion a6130n (Athlon 64X2 2.6GHz, 3GB RAM, 400GB HDD, Vista Home Premium) specs and Desktop specifications - CNET Reviews

What could I get?

You need to open the tower and look at what type of expansion slot it has. The most common type on new computers is PCI-E. It also depends on what you want to use it for.

Jimmy, here is a link to the "Motherboard Specification" page for your rig:

Motherboard Specifications, MCP61PM-HM (Nettle2) 

Scroll down to the section titled "Expansion slots". It shows that you have two PCI, one PCI Express 1 & one PCI Express 16 slots. Now, scroll down further to the "Motherboard layout and photos" section. It will show you where to find the PCI Express 16 slot. This is the slot for your card. I believe that it will be black.

If you have further questions, please let me know.
You can install a GeForce 8800GT