You can't remove the deleted items folder itself, but you can empty it.
Just go into it and select every message in it (or the desired
messages) and hit the delete key. You can use Shift-click to select a
range of messages, Ctrl-click to select any number of messages that are
not "together" or Edit/Select All to select every message.
You can also tell outlook to automatically delete ALL messages in this
folder EVERY time you exit / close outlook, it's an option burried in
the tools menu (don't remember exactly where, use the help function to
find it).
