How to register a new icon for a file type NOT associated with an application

Question

For my filesuffix ".special", I created a new icon and stored it as a file named c:\special.ico.

I also created a new registry value HKEY_CLASSES_ROOT.special\ (Standard) REG_SZ c:\special.ico

After restarting my pc, my file c:\special.ico is listed in the file manager together with the new icon in front of it, but all of my files c:\somefolder\somefilename.special continue to be displayed with the old, default icon.

What do I need to do in order for them to be displayed with the new icon?

Answer 1

It would appear you missed adding the DefaultIcon subkey. Then...

Assign the DefaultIcon subkey a default value of type REG_SZ that specifies the fully qualified path for the file that contains the icon.

From Microsoft Developer Resources - How to Assign a Custom Icon to a File Type

You then have to invoke an icon cache update. Rather than a complete rebuild of the cache, a REFRESH is an easy way to do this by running the following command from the Run dialog.

For Windows 10; ie4uinit.exe -show

For Windows 7 & 8; ie4uinit.exe -ClearIconCache

Answer 2

MS documentation is correct, but misses the per-user (UserChoice key) part. If the Userchoice key exists and pointing to a ProgID, that ProgID will be in effect instead of the one in HKCR\ProgID.

If you can post a file type dump for .special extension, someone will be able to help you better. FileTypeDiag is a nice tool that generates a full report.

Answer 3

CharlieRB and w32sh, Thank you! I particularly appreciate w32sh's link to FileTypeDiag, which seems to be a useful tool I hadn't been aware of.

What DOES work is the text in the MS link, but which is not precise enough; the corresponding example is outright misplaced or even wrong.

When you only want a new icon for a new file type (i.e. one that is not yet associated to some application), you do the following in the registry if the suffix / file type is .x and the full path of the (.exe, .ico or other) file containing the icon is c:\y.ico

In HKEY_CLASSES_ROOT

.x (i.e. you create a new key, which you leave blank, don't leave out the dot, it's part of the key name)

.x\DefaultIcon (you create a new subkey DefaultIcon within your new key .x)

with the following value:

(Standard) (type: REG_SZ) c:\y.ico (no double quotes ("") needed)

After either shutting down and restarting your pc down or simply a user logout followed by user login (a mere user change will be as insufficient as a simple "refresh the registry"), you will then see your .x files, in your file manager, together with their new icon from within the y file. (The same is true after changing the icon without changing the icon file name / location, i.e. when you replace the content of the icon file: Then again the new icon will only be visible after a restart or a user-logout-login.)

Cheers!