How do I reset the application that Windows opens .dat files with?

After installing Index Dat Spy Windows associates all of the .dat files on my computer with the IndexDatSpy program (and in Windows Explorer changes their icon to the Index Dat Spy icon). This occurs with all of the .dat files, not just the index.dat files. Unfortunately this is a "feature" of Windows - it uses only the ".dat" extension for file associations, not the whole file name.

Since most users don't have any other file association for .dat files then this isn't usually a problem. However, if you would like to change the association of ".dat" files with Index Dat Spy, you can without affecting the operation of Index Dat Spy and without having to uninstall it.

The instructions below are for Windows XP. The steps should be largely the same for other versions of Windows.

  • Start a copy of Windows Explorer (not Internet Explorer). Provided you have a Windows style keyboard then a handy shortcut for this is to press and hold the "Windows key", then press and release the 'E' key.
  • Within Windows Explorer click on the Tools, Folder Options menu item.
  • Within the Folder Options dialog, open the File Types tab.
  • In the list of Registered file types scroll down and select the extension "DAT". Beneath the list of registered file types, it will show the current association - described as "Opens with:" followed by the associated application.
  • Click on the Change... button and in the Open With dialog select the application you want to use as the default application for all ".dat" files. Click OK to close the Open With dialog, then Close to close the Folder Options dialog.

That's all there is to it. You can set it back to Index Dat Spy using the same approach.