Why does 3D mapping stop working after installing Google Sky?

Occasionally after installing Google Sky Windows no longer knows how to open 3D maps.

To fix Windows:

• Open My Computer
  
• Go to Tools → Folder Options
  

• Select File type, then scroll down to KMZ / KML and click Restore for each.
  

• When completed the file type should switch from KML file and KMZ file to Google Earth KML and Google Earth KMZ.