I had to leave my system on overnight while I was at work to restore the data from my desktop to the 5400rpm 320gig. When I got home I tried to overwrite the "folder" containing save games to guarantee that nothing went wrong while I was gone, but the program that does that work decided to crap out. I went ahead and hooked everything to the xbox and turned it on and.... bam, there were all my legally purchased XBL games. Started up Marvel vs Capcom 2 and had no problems getting into training mode.
Haven't tried any full disc games yet, so I can't verify that the system a) sees save games properly and b) sees and loads any and all DLC (guitar game tracks) properly. I expect to do that this weekend. I've been really tired this week and thus sleeping a lot.