I did eventually use Vista's tool (after turning off its shadow storage, its hibernation file, crash dumping, and virtual memory, running PerfectDisk multiple times to move special! Windows files from right at the end of the disk ... all this to get around Vista's own limits on how far I could shrink the volume).
I would still like to figure out why gparted isn't working though, because that's a much easier solution if I have to do this again.
make a copy of Vista from your installation. This should be possible after Vista SP1
How would I do this? If you see my other thread in this forum I am having trouble with partimage right now.