a dialog box with outlook express keeps popping up  and says "you have
unsent messages in your out box. do you want to send them now? i have
tried "yes" and "no",but it still continous to come back

You can also go to your Outbox folder, see if there
are any email message still there, and then delete
it/them.

If you have an email in the Outbox folder that has
an incorrect/incomplete email address (for instance)
it will stay in the Outbox folder until it gets fixed
or deleted.

No search; personal knowledge

You likely have some kind of problem with your outbox that causes
messages to get stuck there. So even you answer 'yes' and Outlook
tries to send it again it'll fail and the messages are still there
causing the same popup to alert you again and again.

There's a Microsoft knowledgebase article, Q262052, for Outlook
Express that explains some likely problems and solutions for your
Outbox problem. The URL is:
http://support.microsoft.com/default.aspx?scid=kb;en-us;Q262052

You might also want to browse through the Outlook Express support
pages at Microsoft: http://support.microsoft.com/default.aspx?scid=fh;en-us;oex