FYB
What I meant was go into the start menu and launch your email program, then when it's open, find the options or preferences. Look through the settings for something like "Make this my default email program".
It could be worded in a variety of ways - and many programs will check when they are run and prompt you : "would you like xyz to be your default email program?" or somesuch.
If still no joy, you could always download a copy of Eudora Light, which is free (adware). That should act like I described and hopefully resolve the problem.
Clear as mud! Let us know how you get on.