I bought the Dead Money DLC from Direct2Drive (since it doesn't show up on Steam anywhere) and the zip file was downloaded to my disk. When I unpack it, there are few files including Setup.exe, however when I run it, it starts with Fallout NV product activation screen which of course fails, since I already have it registered (well, it doesn't "fail" per se, it just tells "you have already registered Fallout New Vegas and don't need to register it again") and that's that, cannot install it anywhere or anyhow. File extensions are some "sim" or such so I can't even add those necessary files manually to correct folders. So, anyone knows how the heck can I install this DLC?