This article was previously published under Q166320
If you create a file association between a program and a file extension,you may then be unable to view, edit, or remove the file association fromthe File Types dialog box listing of registered file types.
File associations that are created without a description for thefile type are not listed as a registered file type, even though they dofunction properly.
To change the association of a file type that does not appear in theRegistered File Types list, follow these steps:
In My Computer or Windows Explorer, press and hold down the SHIFT key while you click a file of the appropriate type with the right mouse button.
On the menu that appears, click Open With.
If you are prompted to, enter a description for the file type. In the "Choose the program you want to use" box, click the program you want to use for this file type.
If the "Always use this program to open this file" check box is not selected, click the check box to select it.
Click the OK button.
Microsoft is researching this problem and will post new information herein the Microsoft Knowledge Base as it becomes available.
For additional information, please see the following article in theMicrosoft Knowledge Base:
ARTICLE-ID: 129050 TITLE : Err Msg: The Extension '.<ext>' Is Already In Use By File...