The IClassAccess interface on the Class Store Manager object is used to access class information and binaries during COM object activation. In earlier versions of Windows NT, activation-related lookups occurred in the registry under HKEY_CLASSES_ROOT. To provide support for user-specific application information, this functionality has been extended to maintain class information in the per-user registry key, HKEY_CURRENT_USER\Classes. If the activation information is not found in either of these places, the search continues to the class store. GetClassSpecInfo is called on the Class Store Manager object.
The Class Store Manager looks for the class, interface, or an implementation of these in the list of class stores associated with the user's account. When the information is found, it is used to load, install, and activate the package.