Using a Batch file:
REG ADD "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System" /v "EnableLUA" /t "REG_DWORD" /d "0" /f
Using Powershell:
@powershell Set-ItemProperty -Path registry::HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\policies\system -Name EnableLUA -Value 0