Thanks for the reply Jock1e. I have tried the repair function in the Control Panel and fortunately, it has worked - although none of the saved messages are there. (Whether the Windows 7 repair install or this repair 'knocked them out' I shall never know.)
Fortunately I have recently backed them up, so I should be able to get them back from the external back-up disk.
Incidentally, since this is a portable PC and everything is on the C: drive, can I create a second partition (there's lots of space) on it without 'disturbing' the Windows 7 & applications installation? (If so what's the best way?) If I can, I can then re-direct WLM folders to the new partition and store them there.