[This is preliminary documentation and subject to change.]
Best Practice (Designed for Microsoft® Windows® Logo)
Applications should use component categories. In particular, containers should indicate which standard component categories they support. Also, component categories should be used in preference to adding a key, such as Control, under a component CLSID registry key.
This best practice allows an object to publish its capabilities to other objects.
For more information, see Control and Container Guidelines in the Platform SDK.