In tip 2548 » The Windows 2000 Runas utility, I described the
Runas utility.  Microsoft Knowledge Base Article 294676 contains
the following summary:  In Windows 2000 and Windows XP you can
run programs as a different user than the currently-logged on
user. To do this in Windows 2000, the RunAs service must be
running, and to do this in Windows XP, the Secondary Logon
service must be running. The RunAs and Secondary Logon services
are the same service with different names. This step-by-step
article describes how to enable and use the Run As command on a
Windows 2000 computer or a Windows XP computer.