A nice unadvertised, but logical in its working 'feature' of Media Center is that it will allow the complete playback of a DVD disc including menu's without requiring a DVD disc to be in the drive. First of all you need to remove the layer of encryption present on almost every DVD, to do this you would need to use an application such as DVD Decryptor so you have an unprotected copy of all the IFO and VOB files contained in the discs Video_TS folder.
Depending on which country you’re in changes the stakes of whether it is legal to do that with a product you’ve purchased or not, doing that in the United States you'd probably run foul of the DMCA. After you have your Video_TS folder place it into you’re my videos or shared videos folder\Movie Name\Video_TS
Now when you select the movie name in My Videos it should start to play and navigate as if the DVD is in the drive. You can also add cover art by adding a folder.jpg file into \Movie Name. Particularly useful if you have a very large hard disk kick around that you don’t know what to do with or a region locked DVD drive.