I've partially succeeded in getting a working VM, by doing this:

• A fresh install of Windows in an empty VM, using Greg's proven disk.
• Logging in as administrator, and creating my regular user account (with the same name and pw as on the original machine).
• Installing the VirtualBox add-ins (this failed once, and I had to reboot the VM and run the installer manually; it shows up on a VBox mapped virtual drive).
• Mounting the folder containing the backup file (have to share it first in Ubuntu, then mount it under VBox).
• Using Windows Backup to restore from the backup file. This went smoothly, except that it complained that a couple of system files had been replaced, and would have to be restored from the disk. I re-mounted the installer CD to allow this.

This basically worked, but broke a few things. IE would not run, so neither would Windows Update; I had to manually download the IE7 installer and re-install it (this took ages). Then I was able to run Windows Update, and I'm currently installing SP3.

Delphi runs, but can't open any projects, complaining of an "Invalid install", and saying that Delphi.Personality is not configured. This might be a showstopper, but before I take it on, I'm going to do all the relevant Windows updates and also install .NET, which Delphi needs. If that doesn't work, I may have to do some kind of rescue-install from the original disks.