Update on the problem: we ran
Yasu with the options to clear caches, reset system permissions, and reset Launch Services. It chundered for a bit, restarted, and then we could go in and re-associate Doc files with Word in the normal way. This time it worked, so landlady is happy.
Microsoft were saying "uninstall Office 12.2.0" (SP2), which sounded like overkill to me. I didn't want to go to the console and script anything, since landlady has literally never seen the console, and was already way past her skill level and freaking out. I can recommend Yasu as a nice and friendly way of doing these maintenance jobs. Thanks for the help, Maccums - I promise to be nicer about Macs in future.
