screenSaver.ps1

#Shutdown displays after 5 seconds
#Save as .ps1 and put the script in shell:startup

Add-Type @'
using System;
using System.Diagnostics;
using System.Runtime.InteropServices;

namespace PInvoke.Win32 {

    public static class UserInput {

        [DllImport("user32.dll", SetLastError=false)]
        private static extern bool GetLastInputInfo(ref LASTINPUTINFO plii);

        [StructLayout(LayoutKind.Sequential)]
        private struct LASTINPUTINFO {
            public uint cbSize;
            public int dwTime;
        }

        public static DateTime LastInput {
            get {
                DateTime bootTime = DateTime.UtcNow.AddMilliseconds(-Environment.TickCount);
                DateTime lastInput = bootTime.AddMilliseconds(LastInputTicks);
                return lastInput;
            }
        }

        public static TimeSpan IdleTime {
            get {
                return DateTime.UtcNow.Subtract(LastInput);
            }
        }

        public static int LastInputTicks {
            get {
                LASTINPUTINFO lii = new LASTINPUTINFO();
                lii.cbSize = (uint)Marshal.SizeOf(typeof(LASTINPUTINFO));
                GetLastInputInfo(ref lii);
                return lii.dwTime;
            }
        }
    }
}
'@

$boolCheck = $false

while($true)
{
    if([PInvoke.Win32.UserInput]::IdleTime -gt '00:00:45.0000000')
    {
        if(-Not $boolCheck)
        {
            & 'C:\WINDOWS\system32\scrnsave.scr' @('/s')
            Start-Sleep -Seconds 1
            $boolCheck = $true
        }
    }
    else
    {
        $boolCheck = $false
    }
}