1. Run Windows Mail by clicking Vista’s Start button then choosing All Programs. Then click on Windows Mail.
2. When Windows Mail appears, click on its Tools menu and choose Options.
3. In the General tab, look under the Default Messaging Programs section at the bootm. If the Make Default button next to “This application is the default Mail handler” is checked, Windows Mail should be the default email client on the PC.
4. If the Make Default button is enabled, press it to make Windows Mail the default on your PC.
5. Click OK to close the Options dialog.

It’s also worth checking the default settings in Vista’s start menu …

1. Click on Vista’s Start button then choose the Default Programs option.
2. Choose the Set your default programs option.
3. In the window that appears, choose Windows Mail.
4. Click the Set this program as default option that appears on the bottom right of the window.

After following the procedures above, if Windows Mail should work properly when another application on your PC uses Window’s Simple MAPI service to send emails.