Outlook Express Cannot be Set as Default Mail Client
If you are unable to set Outlook Express as the default mail client and Outlook Express is not available in Control Panel > Internet Options > Programs tab > E-mail: drop-down menu, try re-registering OE as your default mail program:
Click Start and select Run.
In the Open: field, type in the following command and press the Enter key or click OK:
"C:\PROGRAM FILES\OUTLOOK EXPRESS\MSIMN.EXE" /reg
NOTE: Include the quotation marks and the space between the ending quotation mark and the slash (/)reg. In addition, check the path to msimn.exe to make sure that it is correct.
Open Internet Explorer.
Click the Tools menu and select Internet Options.
Click the Programs tab.
In the E-mail: field, select "Outlook Express" from the drop-down menu.