Download and install this hotfix, with Windows Mail not running:

http://support.microsoft.com/default.aspx/kb/941090

Although it's labelled as for mail stuck in the Outbox, it also works in
other folders.

It won't necessarily delete the faulty messages, but should at least make
it possible for you to delete them.

tahitianrose;732443 Wrote:

Hi TahitainRose,

This will help show you how to fix the stuck undeletable email message
problem in Windows Mail for all folders.

Installing the KB941090 update will just fix the problem for now. You
must stop the cause to prevent it from happening again. Read the section
titled "FIRST" in this tutorial about antivirus and other security
programs to help prevent this from happening again, then install the
KB941090 Microsoft Update in the section titled "SECOND" to fix and be
able to delete the stuck message from the problem folder.

'Windows Mail problems'
(http://www.vistax64.com/tutorials/62560-windows-mail-problems.html)

Shawn