I don't think it's the size then. As I said in a previous post, the replays worked on my 20gb official Microsoft HD on my old xbox. The actual usable space on the 20gb MS HD is only about 14gb. The usable space on a 16gb flash drive is about 15gb, so I guess it will only work with an actual HD, and not a flash drive. Guess it's time to crack open my old hd case and put the drive in the x360 slim's expansion port b
Yea i think your right it has to do with having a hard drive(or not), it does'nt read the 4gb, or a flash drive as a hdd.