I finally got around to updating my Home PC so it’s now running Office 2007 Pro (coming from Office 2000 Pro I'm liking it a lot), AutoCAD Architecture 2008 (from 2007), Viz 2008 (also 2007) and I.E. 7 so now I’m in the modern world.
However I.E. 6 put up one heck of a fight to the point where all the tips recommended by Microsoft (which included registry hacks, permission changes etc) didn’t work.
I finally got a clean install by setting up a new user account, logging into it in safe mode, then running the install. Sorted!