Making Outlook Express the Default Mail Handler

Close OE and IE.

Start | Run
Type in:
"C:\PROGRAM FILES\OUTLOOK EXPRESS\MSIMN.EXE" /reg

Press ENTER.

Note, make sure the path to the MSIMN.exe file is as shown above, this is the default installation folder.

A reboot may not be required but to hedge your bets with the registry, reboot.

Now it will appear in the drop down list.