Go to Default Programs, which you can reach either from the
Start menu or the Control Panel, then click the first item: "Set your
default programs."
After a few seconds a list of programs comes up.
Click on Windows Mail. To the right you should then see
"This program has all its defaults."
If it has less than all of its defaults, fix it by selecting one
of the two options indicated by green arrows.
Gary VanderMolen