RUNAS

Execute a program under a different user account.

Syntax
      RUNAS [/profile] [/env] [/netonly] /user:user Program

Key
   /profile   Option to load the user's profile (registry)
   /env       Use current environment instead of user's.
   /netonly   Use the credentials specified only for remote connections.
   /user      Username in form USER@DOMAIN or DOMAIN\USER
              (USER@DOMAIN is not compatible with /netonly)
   Program    The command to execute

Enter the password when prompted.

When you start a program with RunAs /netonly, the program will execute on your local computer as the user you are currently logged on as, but any connections to other computers on the network will be made using the user account specified.

Without /netonly everything will run under the user account specified.

RunAs from Windows Explorer
Select an executable file, Shift-Right-click and select Run As..
This option can be hidden by setting
HKLM\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer
HideRunAsVerb=1

ErrorLevel
The error level (%ERRORLEVEL%) returned by RunAs in Windows XP and above: success=0, failure=1

Examples

   Runas /user:SCOT_DOMAIN\jDoe "mycommand.exe"

   Runas /profile /user:mymachine\administrator CMD

   Runas /profile /env /user:SCOT_DOMAIN\administrator NOTEPAD

   Runas /env /user:jDoe@swest.ss64.com "NOTEPAD \"my file.txt\""

RunAs Reqires the "Secondary Logon" service to be running.

“He who reigns within himself, and rules passions, desires, and fears, is more than a king” - Milton

Related:

AT - Run a command on a remote machine (at a scheduled time)
Aaron Margosis - Running with least privilege
joeware.net - CPAU (Create Process As User) like RunAs but with an options to encrypt the password.
PsExec - Execute process remotely
Powershell: you can run an entire powershell session via RunAs to elevate your permissions.
Equivalent bash command (Linux): SU - Switch User