The Customui sample allows you to customize the Sign In user interface for each Realm by changing the bitmap that is used to brand the user interface, and by changing the text that appears on each screen. This Sign In user interface only appears when you select DPA as your authorization protocol and Membership security as your security for the system.
Each Membership System service provider can upload a customized resource DLL to client computers for each Realm it contains. The client will then be presented with a custom login dialog for the realm when authentication is required.
The source can be found in the directory <sdk install root>\Samples\Microsoft Site Server\PM\customui\