You could try the following command:
runas /netonly /user:yourdoman\youruser "shutdown -s -m \\computername"
The runas command allows you to specify a different user to execute a program that the current user wouldn't have access to. In this case using the /netonly switch targets the remote computer for the authentication.
After executing the above it will ask you for a password for the remote user and it keeps the password hidden from anyone watching.
You can type runas ?
in the command line to see more information for the command.
Also just found this from experts-exchange.com:
In order to remotely shut down a machine, you must be an administrator on the machine you are currently logged on to, as well as an administrator on the remote machine. Even with this condition met, however, remote shutdown may still be disabled in Group Policy (either local, or domain policy). Check the following on the remote machine (or its domain controller if one is present):
* Start->RUN | MMC
* On the topmost menubar, File->Add/Remove Snapin
* Click Add
* Select Group Policy, then click add
* Click Finish, the Close, Then OK
* Click the (+) next to "Local Computer Policy"
* Navigate to the following key:
Local Computer Policy->Computer Configuration->Windows Settings->Security Settings->Local Policies->User Rights Assignment
* Check who is allowed to "Force shutdown from remote system"
The access denied message will appear either because your username/password doesn't exist, you dont have administrator account status on BOTH machines, or Adminsitrators do not have that Right on the remote machine.
You can also get to the Group Policy console by entering gpedit.msc
in the command line.