Continuing the FAT fun saga with an unplanned sequel: rexxfat used partition type 05 instead of 06 for BigFAT, i.e., FAT16 with 2**16 or more sectors. I've fixed this stupid bug in the last rexxfat version. The virtual hard disk image works fine in a Windows 2000 virtual machine:
The odd size 3759 MB matches what I have on a memory card. It's rather tricky to copy the disk image to the memory card, either rawcopy doesn't support copies to a physical device, or it was not obvious for me how to manage this. Using diskpart to unmount the one and only volume on this partitioned memory card wasn't good enough for write access, eventually the diskpart delete volume magic did the trick. Presumably that also explains my difficulties with other tools including dskprobe and HxD.
Looking for explanations I stumbled over SysInternals SDelete. That article doesn't explain how Windows 7 manages volumes on memory cards, but answered another open question: Compressed, encrypted and sparse are managed by NTFS in 16-cluster blocks. That matches my observation for rxsparse.rex, 16×4=64 KB, and if the SysInternals folks got that right Wikipedia also got it right. Hint, it is very likely that SysInternals got it right, after all they were the first to offer a working DOS NTFS-driver permitting write access.