Originally I had 2007 installed when I installed 2010. I got tired of Office starting an installation of 2007 every time I double-clicked a document, so I uninstalled it. Maybe somthing in the registry got altered in some way in that process.

To repair the installation, I use the Add/Remove Programs Control Panel, right? I suppse, if that doesn't work, I should uninstall 2010 and then reinstall it, right? Many thanks for testing.