Privileged Time is the percentage of elapsed time that this process's threads have spent executing code in Privileged Mode. When a Windows NT system service is called, the service will often run in Privileged Mode to gain access to system-private data. Such data is protected from access by threads executing in User Mode. Calls to the system may be explicit, or they may be implicit such as when a page fault or an interrupt occurs. Unlike some early operating systems, Windows NT uses process boundaries for subsystem protection in addition to the traditional protection of User and Privileged modes. These subsystem processes provide additional protection. Therefore, some work done by Windows NT on behalf of your application may appear in other subsystem processes in addition to the Privileged Time in your process.