Thank you very much for your suggestions. I decided to follow this
one first:
I found over 64K files in the directory. In a DOS window opened with
administrator privileges, I ran "DEL *.*", which deleted all files
that weren't in use. That totally solved the problem. Hooray!
In answer to your other question, I used the Windows Mail UI to move
the folders around. I didn't think that was the likely cause because
when I tried a brand new Windows Mail directory, the same problem
arose.
Thanks again - what a relief.
