Did Outlook 2007 ever work on that computer?
You need an Outlook 2007 trouble shooter to carefully go through your setup. You are likely just missing something. The Outlook guide will be the easiest way to figger out what it is... Otherwise the guesswork on this forum will wear you down.
On the top row click Tools and then Account settings, assuming there is anything in the box then double click it and the advanced settings box will come up, you need to check you have things in there such as SMTP and POP information.
Without these Outlook wont know how to send or recieve your mail.
For information on what the settings should be contact your service provider.