Windows 7 Backward Compatibility Update

Microsoft has released an update to the backward compatibility feature in Windows 7 and Windows Server 2008 R2 that promises to increase the backwards compatibility of the operating systems.

The update is not available via Windows Update, only directly at the Microsoft support website and probably Microsoft Download Center as well.

The explanation of the issue is rather technical. It basically resolves a issue where dynamic link libraries (dll) are run in a Windows 7 context even though they have not been designed to be run in that context.

This usually is the case if the dll does not specify an RT_Manifest or where the dll calls an API that uses the dynamic compatibility context.

An update is available to the backward compatibility feature in Windows 7 and in Windows Server 2008 R2. This update enables a dynamic-link library (DLL) that is designed for earlier versions of Windows to run in a Windows Vista context if the following conditions are true:
The DLL does not specify an RT_MANIFEST resource.
The DLL calls an API that uses the dynamic compatibility context. For example, the DLL calls the GetOverlappedResults API.
The backward compatibility feature in Windows 7 and in Windows Server 2008 R2 detects the manifest in a DLL and sets the dynamic context of a DLL to Windows 7 or to Windows Vista. This enables Windows 7 and Windows Server 2008 R2 to provide a Windows Vista context for applications that are designed for earlier versions of Windows.

However, if a DLL is not manifested correctly, the DLL may run in a Windows 7 context unexpectedly. This issue occurs because the Windows 7 compatibility mechanism incorrectly assumes that a DLL is compatible with Windows 7 if the DLL does not specify an RT_MANIFEST resource. This issue occurs especially if all the other DLLs in an application are not manifested or if the other DLLs are manifested with Windows 7 compatible GUIDs. This causes the "faulty" DLL to run in Windows 7 compatible mode. This behavior causes the application that loads the DLL to stop responding. Therefore, customers cannot run an application in Windows 7 context if the application loads at least one DLL in those two conditions.

Windows 7 users who have been experiencing compatibility issues should consider installing the update to see if it resolves the issues they are facing.

There is on the other hand no need to install the update if the programs run fine in the operating system.

The update can be directly downloaded from the Microsoft Help and Support website. Validation is required before the update can be downloaded.

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