Megamaced puts up a good question. You already have the chipset you need, and if there's some specific controller that needs a driver, Dell will mention it. Dell does not make their own motherboards, but they do have custom designs from what I understand, much like HP or Compaq typically have a large company like Asus take a motherboard, change a few things on it (or not, depends) and have a BIOS identifying it as that brand's computer. From what I've seen, Dell motherboard's don't have a 3rd party branding on their parts, so your motherboard may be an enigma.
Now, due to FCC regulations, all parts are required to have a number ID'ing the part, and that will be listed, somewhere along an edge most likely---and on the circuit board, not a chip. You can then take that number, go to the FCC website and look it up. I don't remember exactly where it is as I've only done this with an unknown controller card once, but I do know that it's there.