Article ID: 218805 - View products that this article applies to.
This article was previously published under Q218805
When you double-click an unknown file type, an unexpected default action may occur.
When you right-click an unknown file type, the Open With command may be missing from the context menu that appears.
This behavior can occur if the registry key that handles the command is altered or damaged.
Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:
(https://support.microsoft.com/kb/322756/ )How to back up and restore the registry in Windows
Use Registry Editor to examine the file association key for unknown file types:
HKEY_CLASSES_ROOT\Unknown\shell\openas\commandThe "default" value for this key should read:
C:\%windir%\rundll32.exe shell32.dll,OpenAs_RunDLL %1If necessary, modify the value to match the value shown here.
For additional information about how to determine which folder Windows is installed in, click the article number below to view the article in the Microsoft Knowledge Base:
(https://support.microsoft.com/kb/305792/EN-US/ )How to Determine Which Folder Windows Is Installed In
Article ID: 218805 - Last Review: January 24, 2007 - Revision: 1.3