Set or Change File Associations & Extensions in Windows 7 And Windows 8.1
Each file in your Windows operating system has an extension in its filename eg. .txt, .doc, etc. These extensions are used to identify the program, with which, windows can open this file. You can set or change these file associations in your Windows. In Windows XP you had this setting to change file type associations in Folder Options. In Windows 8, Windows 7 and Windows Vista you don’t see it there, though.