The last time WLM tried to compact my folders, I got the following error message:

The folder is currently in use by windows live mail or by another application

Searching on this forum, I found someone with a similar problem and tried the fix outlined here but it didn't help.  :-(

http://answers.microsoft.com/en-us/windowslive/forum/livemail-program/why-does-windows-live-mail-offer-to-compact-files/2e973760-0d5e-4ff1-a305-4a19123ed97d

Anyone have a better idea?