Access is denied when attempting to shutdown another computer using the shutdown command:

shutdown.exe /s /m \\COMPUTERNAME /t 00

Result:
COMPUTERNAME: Access is denied.(5)

Enabling Windows 8 Remote Shutdown from command.

I am using this solution on a home workgroup local network. The solution works for shutdown.exe and psshutdown.exe. It works for Windows 8 and should work for Windows 7.

CHANGE THE FOLLOWING SETTINGS ON THE REMOTE COMPUTER:
Control Panel, Network and Sharing Center, Change Advanced Sharing settings
"Private" enable "Turn on File and Printer sharing"

Add Registry Key

RUN regedt32.exe

Goto:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System

Right click and add new DWORD

"LocalAccountTokenFilterPolicy"=dword:00000001

When user name and password are not the same on both computers change the following on the remote computer:
Change Local Security Policy

RUN secpol.msc

Local Security Policy, Security Settings, Local Policies, User Rights Assignment
Add "Everyone" to "Force shutdown from a remote system"