1.  Go to Messages and click the link  (Listed in the menu on the left hand side of the Forum)
2.  Scroll to the bottom of the screen
3.  Type your user name in the "SEARCH" field (You can use my username as an example: rhomes, but
    you only have authority to delete your own posts)
4.  Hit enter or hit the Search Button
5.  You should see a listing of all your posts
6.  Click the subject that you want to delete.  The subject is highlighted in blue
7.  This will take you to the body of your message
8.  Look for the Delete button (It is beside the Reply and Forward Button)
9.  Hit Delete
10. This will take you to another screen where you will need to confirm that you want to delete your
    message.
11. Hit Delete Topic to confirm
12. Your done!

http://groups.yahoo.com/group/greybrucefreecycle/files/Deleting%20Posts 

--- In greybrucefreecycle@yahoogroups.com, "threenans" <threenans@...> wrote:
>
> Does anyone know how to remove all posts that are no longer valid...I
> would like to clear out all mine that are not available any
> longer..thanks...
>