This is what worked:

• Made a fresh build of XP using a 200GB expandable drive in VBox, and using the volume licence installer.
• Did all Windows updates.
• Connected to the Windows Backup file on the Ubuntu Host, and used Windows Backup to restore as much as possible.
• Exported the HKEY_CURRENT_USER and HKEY_CLASSES_ROOT hives on the original machine (logged in as myself), and then imported this into the registry in the VM (logged on as admin(. Some in the latter hive failed due to keys being locked, but most things succeeded.
• Ran Delphi 2005. It didn't know about any of its components, so I had to go to Components / Install Packages, and install all the .bpl files in the BPL directory (this was easy because I'd specified that this be in a separate location in Delphi).
• Started Delphi successfully, and discovered that the PATH was missing most of the PAS file locations, so I had to add them all manually until everything was found. Eventually I was able to compile Transformer and the IMT.

Today I installed Delphi 2009, and all the updates, and then started adding 3rd-party components. I have the latest JEDI JCL and JVCL installed and working, and I'm now looking at Graphics32, which is causing me problems, since there's no D2009 package for it.