When you open Default Programs applet, and click Set your default programs link, Windows Mail may be missing from the list of programs.
To reinstate Windows Mail entry to the default programs listing, download mailclients.zip, unzip the contents to a folder, and run the mailclients.reg file. If you are prompted for an administrator password or confirmation, type the password or provide confirmation Click Yes to continue.
About the author
Ramesh Srinivasan founded Winhelponline.com back in 2005. He is passionate about Microsoft technologies and has a vast experience in the ITeS industry — delivering support for Microsoft's consumer products. He has been a Microsoft MVP [2003 to 2012] who contributes to various Windows support forums.