Defining your Email Program in Vista - Windows Mail

Click Start/Default Programs (Default programs is on the right hand side of the small window)
Click Set your default programs.
On the left hand side of the new screen Click Windows Mail
On the right hand side Click - Set this program as default.
Click O.K.
Should the above not work then we must go deeper follow these steps
Start/Default Programs
Choose defaults for this program
make sure all boxes are ticked (eg. eml, mailto, email link) Click Save
Close down and restart your computer

Defining your Email Program in XP - Outlook Express

Open Outlook Express.
Click Tools on the toolbar
Click Options in the drop down list
Click Connection
Click Change
Click Programs
Make sure Outlook Express appears in the email box. If it is not there click the arrow on the right side of the box and select Outlook Express from the drop down box.
Click O.K.
Close the Program