Can not delete message from my deleted message box…Using Windows live mail-2012

I have just gone back to windows 7 from windows 10 due to my printer not working using windows 10.  Once the transaction was complete I went to my windows live mail 2012 where I started to review my messages and deleting a few.  I then went to my delete box and tried to delete the deleted messages from my computer.  I get a message, "message not found" on the head of the message itself.  Once I click delete I get another message stating "unknown error".  But the title of the message still appears.  Any help out there?  Would appreciate it.