I've seen questions related to Microsoft Outlook not showing up in the Vista Default Programs list. I have tried Detect and Repair, Reinstallation, and the OL2003Fix that is often suggested. All provide no joy.
Microsoft Outlook does appear in HKLM\Software\RegisteredApplications. But it does not show up in the Default Programs list. Two other programs don't show up in the programs list: Windows Mail and Windows Mail (News).