For any file in that condition I use Unlocker

Found here: http://ccollomb.free.fr/unlocker/

It has many other flavors:

Cannot delete file: Access is denied
There has been a sharing violation.
The source or destination file may be in use.
The file is in use by another program or user.
Make sure the disk is not full or write-protected and that the file is not currently in use.

At the bottom of my Pegasus screen I can read "1 queued". Despite the fact that I checked "Send mail at once, without placing in queue". Indeed If I open "Review queued mailk" there is an email. It probably/possibly got there bacause I mistakedly sent of a mail without any address. My problem is that it seems impossible to get rid of this mail. If I try to delete it from within the "review queued mail panel" it seems to be gone but there is still "1 queued" listed at the main screen. If I open the "review queued mail" panel again, it has reappeared. With the original date and time information"!! If I open it from the Review panel, add an address and send it, it seems to start by copying itself because there is now a Message 2 in the queu (again without an address). I could live with this but it is probably somehow related to another problem that started about the time I got this sticky queued mail. I want to get rid of it as a first part of solving that problem. (See "What info goes to the SMTP server"?)

Hello Jon L.,

Try this solution:
- Use Help | About Pegasus Mail | Info to locate the HOME mail directory.
- Use File Manager or Explorer and go to this directory and delete the zero length PMO, PMX and PMW files.

There were several .PMO files. All 1kB long. There was one .PMX file. 0 kB long (26D48570.PMX). There were no .PMW files. When I tried to delete the .PMX file Windows claimed it was in use and did not allow me to delete it. (Pegaus was closed at this point). Next step?

[quote user="JonL"]There were several .PMO files. All 1kB long. There was one .PMX file. 0 kB long (26D48570.PMX). There were no .PMW files. When I tried to delete the .PMX file Windows claimed it was in use and did not allow me to delete it. (Pegaus was closed at this point). Next step?
[/quote]