Are you kidding me? You can rent them straight through the market place, also with media center the XBOX as an extender can play mv's using divx on the host PC. I have 4 xbox's in my house I use as an extender and a seperate host media center PC that shares out all of my movies music and TV. Three of my four xbox's are set to boot straight into the media center app.
My xbox will probably RRoD soon anyways ha.