Thanks for providing the SOFTWARE and SYSTEM hives.  Firstly the
SOFTWARE hive has an unusually large 'nk' node, which required me to
increase one of the limits in hivex:
https://github.com/libguestfs/hivex/commit/bec3f0bb632c4b84a1dfb73eb6333c...
The SYSTEM hive was even more interesting:
  $ hivexsh system
  
  Welcome to hivexsh, the hivex interactive shell for examining
  Windows Registry binary hive files.
  
  Type: 'help' for help summary
        'quit' to quit the shell
  
  system\> ls
  ControlSet001
  ControlSet002
  LastKnownGoodRecovery
  MountedDevices
  Select
  Setup
  WPA
  system\> cd ControlSet001\Services
  system\ControlSet001\Services> cd Firstboot
  hivexsh: cd: Argument list too long
This was the error seen in the conversion, and it turned out to be
caused by the hive containing a node which contains a French name,
encoded in UTF-8.
This is a bit more complicated to solve ..
Rich.
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