I've installed the second disc and yet when I run the game the downloads don't show up, I exited and tried to re-install it but, as it took only a few seconds to say completed, I assumed that the DLC has infact already been installed. Does anyone know why it's not showing up in the game?

Did you activate the DLC files in the Data Files section of the game launcher?

You know... I think you might be onto something...