Did you accidentally use Default Programs or the Open With dialog to associate .exe file types with some application, causing every program to open in that chosen application? Windows provides no option to reset the .exe file associations, and you’ll have to do this manually. For example, one of our readers accidentally associated executable files using Notepad, and this caused Notepad to open every time when a program was launched.
When you use the Open With dialog to associate .exe files with another application, the settings are stored in the following registry key:
There will be a value named Progid in the right pane. The Progid data will contain the application’s exe file name (Applications\Notepad.exe, Applications\IExplore.exe, or a Programatic Identifier such as txtfile, jpegfile etc).
Note that despite this problem, you should be able to launch applications by double-clicking on the data files. For example, with the above setting, you should be able to launch Microsoft Word application by double-clicking on a .doc file, but not by running Winword.exe directly.)
You need to delete the UserChoice key above using a REG file or a script. Download exefix_cu.reg, and save it to Desktop. Right-click on the REG file and choose Merge.
(Hint: To undo the Open With setting for other file types, the registry location is the same. Replace the text .exe in the above registry path with the actual file extension.)
Where .xyz is the file extension for which you want to undo the Open With action.