I went into BIOS and disabled the "HD Audio Controller" and Realtek disappeared off the Device Manager but there still isn't a sign of the Card.
Hmm, I thought for sure that would fix it. Well, I can only think of 2 more things, neither of which are good. Either the card itself is bad or the PCIe x1 slot that you put it in is.
It SHOULD have been detected even with the Realtek Audio enabled, honestly, but that was worth a try.
Can you try it in another system?