File Type association is one of my interesting subjects in Windows. File types that are not registered with the system and files that have no extension, are assigned a generic icon from shell32.dll,0 resource by default in Windows. This is the case in all Windows Operating Systems.

When working on a different problem with the registry, I found that the unknown or generic icon for unregistered file types and for files with no extension can be customized as per your choice in Windows Vista. If you’re using Windows Vista, you don’t have to see the boring icon any more! This post tells you how to override the generic icon in Windows Vista.

Windows Vista stores the icon setting for unknown file types and extension-less files in this registry key:

The (default) or the unnamed value points to the following icon resource by default:

Using the Registry Editor, you can change the (default) value so that it points to an .ico file that you already have, or a icon resource inside a DLL or EXE file by mentioning the file name and Resource Identifier.

Using the Icon picker (a.k.a. the Change Icon dialog), I spotted a relevant icon in shell32.dll, 224 that can be assigned for unregistered and extension-less files. You just need to replace the existing Value data (%SystemRoot%\System32\shell32.dll,0) with %SystemRoot%\System32\shell32.dll,224 using the Registry Editor or using the REG files below.

REG FILES TO AUTOMATE THE ABOVE

1. Download unknown-icon.zip and save it to the Desktop.

2. Unzip the archive and extract the files to a folder.

3. Right-click on the file custom-icon.reg and choose Merge.

4. Click Yes when asked for confirmation.

5. Restart Windows so that the change takes effect.

Here is how it looked before:

We’ve changed that to:

Tip: In case the icons don’t automatically refresh even after a reboot, you can force a shell icon refresh.

Editor’s Note: I haven’t seen any side-effects of this tweak in my Windows Vista PC. Only caveat that I can add is that if a third-party application in your system uses the same shell32.dll,224 icon for one of its file types, it may become difficult to differentiate unknown or unregistered file types from the proprietary file type used by the third-party application.

There is indeed a way to change the unknown icon in Windows XP. I’m not posting that now because I experienced a minor issue (cosmetic) when doing so in Windows XP.

UNDO INFORMATION

To restore back to the factory default icon that’s shown for unknown and unregistered files, apply the default-icon.reg file which is enclosed in the Zip archive above.