Ok, I can do that.
Windows XP and Windows Media Player do not come with any way to play DVDs. Most new systems come with PowerDVD, including mine, but if you happen to do a fresh re-install of Windows, then suddenly get sent to an out-of-state convention by your company, you might not have any way of playing DVDs. If you have internet, as far as I can tell you are screwed.
I downloaded the K-lite coded pack (full, don't know if basic will work). The thing I missed, which is why I was confused because this solution had worked before, is the checkbox during setup that has the DVD codec, as well as a list of which codec you want. I picked Cyberlink, because I know it works, and viola! The DVD works like a charm. I don't know why WM is so stupid they don't include any codecs with the player, but oh well.