Right norm some where along the line.. The access Defaults have buggered up. To rectify the problem..
Then under Control Panel click "Set Program Access And Defaults"
Then click "Custom"
Then click "Choose a Default Web Browser"
Then click "Internet Explorer"
then Click "OK"
NOTE: Make sure internet explorer and outlook express are closed before doing the above..
Then try outlook express again..
If that doesnt work then its a Registry Issue which if you like i could fix for you