The filesystem on the 360 is slightly different then the file system on the original xbox. The xbox 360 harddrive has a partition (partition 3) formatted with the original xbox's file system so it can hold original xbox saves. However, the memory card is formatted in the 360's file system so it can not hold original saves. It may be possible to format the 360 memory card with the the original xbox's file system but most likely the 360 would not be able to deal with it.