User Time is the percentage of elapsed time that this thread has spent executing code in user mode. Applications, environment ...

% User Time is the percentage of elapsed time that this thread has spent executing code in user mode.  Applications, environment subsystems, and integral subsystems execute in user mode.  Code executing in user mode cannot damage the integrity of the Windows NT Executive, Kernel, and device drivers.  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 might appear in other subsystem processes in addition to the privileged time in your process.