Ok I looked over my computer and took a little info down about it. It looks like in the rear of the computer I have two expansion slots.
In one of them is some type of card though Im not sure exactly what. It has a teal-colored background in a spot where some type of 9-pin (5 on top, 4 on bottom) connector goes. It also has a spot for what looks like a S-Video cable on it. So there is one expansion slot left in the rear of the computer.
I took a look inside my computer and on the motherboard I only saw two slots. I know its terrible, but keep in mind its the "small form factor" version of a Dell Optiplex GX620. Anyways one was PCI-E and the other was PCI. I hope this helps.
Also note this: I know I should probably get a bigger computer, but at the moment I am pretty short on cash am looking just to get an upgrade for now.