Every file in the Windows has an extension which identifies the file and associates itself with the programs, such as .txt for text (notepads) / .doc for (documents) etc. These extensions represent the default program which will open that certain file.
At times; you may need to remove the file extensions or change them; the Windows Vista and Windows 7 does not offer a built-in GUI utility to remove the File Type Associations.
BUT you can easily do this with a program called “Unassoc.exe”.
In order to continue; please follow the steps below:
1) Download and install the tool unassoc_1_4.zip
2) Extract the zip file and open the unassoc.exe file
3) You can choose the extension from the list; or search it in the file types (field) and then choose “Remove file Association (User)”.
4) After it has been removed; the specific file will needed to be re-associated which is easy when you open the program; windows will present you with an option to choose a program to open the file with.
5) This program will help if files have been associated incorrectly.