This 4 part series will discuss the Windows access control model and how it is implemented in Windows NT and 2000. In this 2nd article we will start programming with security identifiers, access control lists and security descr iptors. We will solve trivial problems using the SID, obtain information from an access token, enable a privilege, fill up an access control list, and finally we will check if we have access to a resource. The demo project provided is a Whoami clone written Windows 2000 style. The source code includes equivalent programs of the article s code written with the Low level APIs, the Windows 2000 APIs, and the Active Template Library.