In Windows, each file extension has an associated program that is used to open it. If you double click on a file and nothing happens, then the program that’s called when a file with that extension is opened is not installed or configured correctly.
The main configuration files involved in setting these associations are:2
1. HKEY_CLASSES_ROOT (HKCR)
2. HKEY_CURRENT_USER Software Microsoft Windows CurrentVersion Explorer
3. HKEY_LOCAL_MACHINE Software Microsoft Windows CurrentVersion Explorer
4. HKEY_USERS .DEFAULT\Software\Microsoft\Windows\CurrentVersion\Explorer
The information about a file extension is stored in the registry under these two keys:
HKCR\.extension\ (for example, HKCR\txtfile\shell\open\command)gold rates
(for example, HKEY_CLASSES_ROOT\.txtfile\shell\open\)
Files with the same extension are usually grouped into a single class, with its information stored under HKEY_CLASSES_ROOT\. The default classes for most file extensions are:
HKEY_CLASSES_ROOT\.txtfile (Default) = txtfile
HKEY_CLASSES_ROOT\.txtfile\DefaultIcon (Default) = txtfile.exe,1
where txtfile is the name of the class and 1 is some kind of identifier for Windows.
To see which program(s) are configured to open a particular file extension, try this:
In Windows Explorer, click on the Tools menu and choose Folder Options.
Click the File Types tab. In the Registered File Types list box, scroll down until you find your file extension. If it’s shown in boldface type then that means its associated program is listed below. For example, you can see that .txt is associated with Notepad.
Now click on the Advanced button. If your file extension isn’t shown in the Registered File Types list box, then it’s not registered and you’ll need to add it by hand (see below).
If the associated program doesn’t seem to be working properly, try changing its properties according to the following steps:
In Windows Explorer, right-click on the file that is not opening and choose Open With. In Windows 7, you can also click on a file and choose Open With from the menu that appears after right clicking once.
In earlier versions of Windows, you’ll need to choose More Apps first if your list is empty.
In most versions of Windows, you can right-click on a file and choose Open With to see the list of programs associated with that extension.
Click once on the program name in the list that opens, then click on Remove. Click Yes if Windows asks whether you’re sure.
Now try using Open With again as you did before to choose a program from the list. This time, click on Browse and find the program that you want to use.
Usually Windows will install programs in C:\Program Files (x86)\ and their folders will be named according to the program name.
Some programs like Adobe Reader may be installed somewhere else such as C:\Program Files\Adobe\Reader or C:\Program Files (x86)\Adobe Reader.
If you cannot find the program, then it may have been installed somewhere else on your hard disk and that’s fine too. You can see what programs will be listed by default by clicking the Default Programs button in the Windows Control Panel.
After finding the program that you want to use, click on Open.
If Windows asks whether you’re sure you want to change the file association settings for this extension then answer Yes or Continue.
You will see a message explaining that you are configuring this program to open new types of files. Click OK and proceed as usual if it says something like “This program has been configured to open 5 extensions”.
If you want to change the file association settings for this program only once, then if Windows asks whether you’re sure that you want to always use this program with this extension then answer No. This message will only come up again if there are other files or subfolders with the same name or in the same folder.
If you want to change the file association settings for this program every time, then answer Yes when Windows asks whether you’re sure that you want to always use this program with this extension. This message will only come up again if there are other files or subfolders with the same name or in the same folder.
If you use a file association management program like Default Programs Editor, then this will remove all of your custom associations and set the default one again.
This is because Windows doesn’t give any priority to these third party programs for file associations.
You can make it work by either editing the registry yourself or using another method such as Portable Default Programs Editor or Default Programs Editor which are programs designed for this purpose.
Otherwise, installing the program with the file association will keep your custom associations even if you uninstall it later on.