This article was previously published under Q257592
In Microsoft Windows NT 4.0, all entries specific to file type associations are stored in the following registry key:
HKEY_LOCAL_MACHINE\SOFTWARE\Classes (HKEY_CLASSES_ROOT is an alias of location)
For computers running Microsoft Windows NT Server 4.0, Terminal Server Edition, you need the Peruser tool to allow these settings to be copied to each user profile so you can configure this information on a per-user basis.
In Windows 2000 and Windows Server 2003, a new location is added for storage of user-specific file type associations in the following registry key:
This location allows for unique customization of file type associations in the user's profile, without having to duplicate information in multiple registry locations and unnecessarily increase the registry size.
In Windows 2000 and Windows Server 2003, information stored in the HKEY_LOCAL_MACHINE\SOFTWARE\Classes registry key still contains global file type associations that are global to all users of the computer. However, entries that reside in the HKEY_CURRENT_USER\SOFTWARE\Classes registry key take precedence in the event of a duplication.
The user interface (UI) still points to the global settings in the HKEY_LOCAL_MACHINE\SOFTWARE\Classes registry key. In addition, security is changed so that only members of the Administrators or Power Users group have permissions to this dialog box. This affects workstations, servers, and servers in Remote Administration mode.
On computers running Windows 2000 Terminal Services in Application Server mode, the UI may be locked down so that no one can change file type associations (not even administrators). This is done so that you can only edit the entries programmatically or by using MSI-based applications. This ensures that an inadvertent change in the UI does not effect the global file type associations across the computer running Terminal Services and all of its users. When this policy is enabled, the New, Delete, Change, and Advanced buttons are unavailable on the File Types tab of the Folder Options tool in Control Panel.
You can enable this functionality by changing the following registry entry:
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:
322756 How to back up and restore the registry in Windows
Changing this key from its default value of 00000001 enables the File Types dialog box to function just as it does for other Windows 2000 configurations. Administrators and Power Users can change the global file type settings for the computer and all of its users.
Currently, there is no way through the UI to change or edit the user-specific file type associations stored in the HKEY_CURRENT_USER\SOFTWARE\Classes registry key. If you want to do this, you have to directly edit the registry or develop your own UI to gain access to this information.
For more information, search on HKEY_CLASSES_ROOT in the Technical Reference to the Windows 2000 Registry in the Microsoft Windows 2000 Resource Kit.
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