tried a couple more times but it failed. Went ahead and did an erase and install. Upgraded the system files, but not any application upgrades.
Tried the Parallels install and it worked straight away
The Repair Permissions "hang" was not a hang! The blue progress bar stalls at about 25% of the way, saying "Estimated time: Under a minute". But, after five minutes or more, it starts to move again and says "Estimated time: about 8 minutes". And carries on to completion.
Now to get a new set of Windows discs. I had hoped to install the XP stuff from my old Virtual PC discs, but I've lost the Activation Code, and anyway I can't seem to extract just the XP without the installer wanting to inatall Virtual PC.
Haven't seen any XP discs around lately. Is Vista really as bad as people say?