Thanks! This idea worked - I was able to recover the key I needed. I hit a few gotchas along the way... The user registry has moved, as of Vista. But a bit more googling found that the locations of the various hives are given in Wikipedia (
Windows Registry - Wikipedia, the free encyclopedia ) if I'd only thought to look there. And for whatever odd reason, once I'd mounted the VHD using Computer Management : Disk Management : Attach VHD, I was unable to copy the
Usrclass.dat file from the mounted VHD to another drive. But since the VHD I had mounted was a copy anyway, I just did the Load Hive directly off of the mounted VHD. And "Load Hive" only works into HKU or HKLM, so I just added the hive into HKU.
Many thanks to pjhutch!