THIS CORRECTS MY EARLIER POST, WITH APOLOGIES FOR CONFUSING ANYONE.
I am running Vista Home Premium 32, and using Windows Mail version 6 that came pre-installed. No significant problems for the 4 years I've owned this setup.
But, to keep from taxing the mail program size limits, I've just exported some of my older mail folders using the Export command in the Mail program to a directory I created in My Documents. Then as a test and to re-read just one message, I tried to REimport one folder using the Import command. At that point I noted that the Mail program (labeled as Windows Mail 6 as I said above) invited me to import in the format of Windows Mail 7, without offering me the option of Windows Mail 6. The other options did not look helpful either - I don't use Outlook, for example. So Q1 is: do 6 and 7 have the same or at least compatible file formats such that this is actually not likely to be an issue?
Then I tried to import anyway using the Windows 7 choice, and was told that the folders had the wrong format. Perhaps that answers Q1. Regardless, my Q2 is: what went wrong here? Maybe it's got nothing to do with file type and something to do with saving to My Documents?
But Q3 is, of course, how can I recover those folders when I need them?
I'd appreciate guidance that does not suggest use of a different mail program. Windows Mail has worked well enough.for a long time.
Just in case it affects anything, I am using MSE for protection, and it's up to date.