outlook express delete mail error

Sounds like the message is corrupted. If you can move it to a different folder, you should then be able to delete the folder. You may need to do this in Windows Explorer by deleting the foldername.dbx file, but this may also require you to delete the folders.nch file to see that the folder is gone. If you do this, all your nice nested folders in OE will be back to a flat file structure. Tedious, but not terminal.
If you can't move it, create a temporary holding folder and move all the other messages in the bad messages folder into it. This should leave the original folder with the bad message in it, which you can delete the way described above. If this is the Inbox you have deleted, OE should recreate it. If it is a different folder, you will need to recreate it again, then move the messages from the temporary folder back into it.
Hope this helps.
Brett.