In pre-Vista versions of Windows Media Center, DVDs you ripped to your hard drive with programs like DVD Rip would show up for playback in the My Videos folder. For whatever reason, Microsoft decided to disable this feature in Vista as a default, requiring a registry edit to get it working, as detailed in the linked Microsoft support page below. To be perfectly honest, though, despite making this registry edit, I'm still having trouble accessing my ripped DVDs with Vista Media Center even after making this registry modification, so if you have any luck, share your experience in the comments. I'm also very curious to know if this will allow you to stream ripped DVDs to your extenders, particularly Xbox 360 extenders, so let's hear how it's working for you. Thanks jtimberman!