Fixing incorrect file associations
If somehow the default program associated with a file gets corrupted or changed to another program then any files that belong to that program would not run! Apart from problems with .exe file extensions you can use the registry editor to undo any other incorrect file associations. In cases of .exe file association problems you can read a previous article titled Filename extensions – Can’t open .exe files? since, using the procedure below would not allow you to open the registry editor to resolve .exe file association issues!
To start the registry editor, type regedit in the Start menu search text box and press enter. For instance, to undo an incorrect .cmd file association, open the Registry Editor and delete the following key:
Then, next time you double-click on a .cmd file, this registry key will be regenerated and the file association behaviour for .cmd will return to its default.
A word of caution – incorrectly editing the registry may severely damage your system. The above modifications are intended for Windows advanced users who are familiar with the registry editor. Users are also reminded to backup the registry before making any critical changes.