Prevents users from changing the default programs for messaging tasks.If you enable this policy the E-mail Newsgroups and Internet Call options in the Internet Programs area appear dimmed. To display these options users open the Internet Options dialog box and then click the Programs tab.If you disable this policy or do not configure it users can determine which programs to use for sending mail viewing newsgroups and placing Internet calls if programs that perform these tasks are installed.The "Disable the Programs page" policy (located in \User Configuration\Administrative Templates\Windows Components\Internet Explorer\Internet Control Panel) which removes the Programs tab from Internet Explorer in Control Panel takes precedence over this policy. If it is enabled this policy is ignored.
Windows Components\Internet Explorer
User
At least Internet Explorer 5.0. Not supported on Windows Vista
HKCU\Software\Policies\Microsoft\Internet Explorer\Control Panel!Messaging
inetres.admx