Where is USRMGR.EXE in NT Workstation?

A. Windows NT Workstation does have a User Manager tool use for managing local machine users and groups however its not the same tool that is used on domain controllers.

The User Manager that workstations use is called MUSRMGR.EXE however you could copy over USRMGR.EXE from a domain controller to enable domain user/group management from a workstation.