I was dutifully pissed when I found out my Xbox 360 RRoD "fixer" (courtesy of ebay) had a bricked DVD drive and the original key was lost forever.
To explain: the previous owner tried to mod the DVD drive firmware and messed up. This hosed the DVD Drive and possibly the one piece of data that would allow me to swap for a different drive. Basically, every 360 motherboard is "married" to it's original DVD drive via special encryption keys. Without a proper key match, the console will no longer play Xbox 360 disc games. Even though I managed to pull the key off the bricked drive, it was not a match, so it's no good.
At least, that's what I thought.
Even though it will not play 360 games, I can still watch DVD movies with it. It still works with Netflix. For games I can download XBLA games to a storage device and play them. Lastly, the pseudo media center functions of streaming music and videos still work. It went straight to the kitchen, ending up being a good investment of about $80 ($50 for broken 360/power supply and $30 for a new DVD drive). I must say it's much better than the PS2 that used to be in there ;).