🙂 Many thanks. The heyday of this particular sort of problem was 4-5 years ago, so the Google results are buried way down (if they are there at all ...). Those results won't be of so much help either, because the pref files are stored in different locations on Vista and 7, and the format of pref files has changed since version 7.0 ... etc etc ...
We're going to try a pref file rebuild. For the basic technique, see the "Remove iTunes preference files" section from the "User-specific troubleshooting" section of the following document:
iTunes for Windows Vista or Windows 7: Troubleshooting unexpected quits, freezes, or launch issues
Prior to doing the preference file rebuilds:Best to make a note of any custom preferences you have set up for your iTunes. (Rebuilding pref files returns preferences to their defaults ... so you'll likely have to set some of those custom preferences up again from scratch.) Also make a note of any third-party plugins/add-ons you have installed. You may have to reinstall those after the rebuilds.
Things to watch out for during the rebuilds
Rebuilding the preference files in the \Local\ location causes the iTunes license agreement to run. So you'll need to agree to that again.
Rebuilding the preference files in the \Roaming\ location causes the iTunes Setup Assistant to run. When prompted to do so,do notadd files to your iTunes library. (Otherwise you'll end up with a library full of duplicates.)