Try this in Internet Explorer, Tools>Internet Options>Programs tab, under Internet Programs for E-mail, hit the drop down arrow and select Outlook. Hit Apply, OK. Test it by selecting my Send me a message Icon above. Click on my e-mail address and Outlook should load a new message with my e-mail.
In Outlook Express, Tools>Options>General tab, at the bottom of the page you should see This Application is NOT the default mail handler.
Also, it should say This Application is the default news handler.