Large Email Stuck in Outlook Outbox

I'm using Outlook 2003 on a computer running Windows XP Home.  I tried to send an email with an attachment.  A PDF file so I did not consider the size, but it was multiple pages and very large (over 18mb).  It will not send, but I cannot delete it.  Every time I try, I ether get no response at all, or it tells me that Outlook is already trying to send the email.

How do I get rid of this email?

Thanks,  Tim Golike