I assume you are running WinMail in Vista?  It's a known bug, ESPECIALLY with Norton.  Norton does NOT like WinMail (or Vista) and will lock up your delete program.  Run the fix, uninstall Norton (use the Norton Removal Tool to get it all).  You need to get another virus program.  I've had good results with McAfee 2008 10-in-1 ISS.  You might also want to consider changing mail client apps.  I'd suggest Windows Live Mail - works like, looks like, WinMail, OE. etc. only has more features.  Free download from MSN.  Companion product to also-free Windows Live Messenger.
Bob, Still Old, Still Grey, And Still A Woolf

No trees were harmed in the sending of this message and a very large number of electrons were asked their permission to be terribly inconvenienced. And a party was thrown for them afterwards for being really cool about it.

Bob's Space - Home Page of the Olde Greywoolf

 "ps" <ps@discussions.microsoft.com> wrote in message
 news:C5E8CF4B-B892-48C9-870D-EF6A8AF34FF9@microsoft.com...
 >I am unable to delete messages in my outbox and junk email box.  The
 >message
 > says an unknown error occured.  When I tried to do the process from
 > another
 > post it didn't work.  how can i fix this problem.

 Unknown errors and undeletable messages in Windows Mail are usually due to
 interference from an antivirus peogram.  What if any antivirus programs do
 you
 have?

 For a temporary fix, 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.  If you don't know whether you have a 32-bit version
 of Vista or a 64-bit version, try the hotfix for the 32-bit version first.
 The Vista SP1 update also contains this hotfix, but takes longer to
 install.