PreventSleep.ps1

[void][System.Reflection.Assembly]::LoadWithPartialName("System.Windows.Forms")

Add-Type -TypeDefinition @"
using System;
using System.Drawing;
using System.Runtime.InteropServices;
namespace System {
	public class IconExtractor {
		public static Icon Extract(string file, int number, bool largeIcon) {
			IntPtr large;
			IntPtr small;
			ExtractIconEx(file, number, out large, out small, 1);
			try { return Icon.FromHandle(largeIcon ? large : small); }
			catch { return null; }
		}
		[DllImport("Shell32.dll", EntryPoint = "ExtractIconExW", CharSet = CharSet.Unicode, ExactSpelling = true, CallingConvention = CallingConvention.StdCall)]
		private static extern int ExtractIconEx(string sFile, int iIndex, out IntPtr piLargeVersion, out IntPtr piSmallVersion, int amountIcons);
	}
}
"@ -ReferencedAssemblies System.Drawing

$ES_AWAYMODE_REQUIRED = [uint32]"0x00000040"
$ES_CONTINUOUS = [uint32]"0x80000000"
$ES_DISPLAY_REQUIRED = [uint32]"0x00000002"
$ES_SYSTEM_REQUIRED = [uint32]"0x00000001"

$ste = Add-Type -memberDefinition @'
[DllImport("kernel32.dll", CharSet = CharSet.Auto,SetLastError = true)]
public static extern void SetThreadExecutionState(uint esFlags);
'@ -name System -namespace Win32 -passThru

$contextMenu = New-Object System.Windows.Forms.ContextMenu
$menuItemEnable = New-Object System.Windows.Forms.MenuItem -ArgumentList "Enable"
$menuItemExit = New-Object System.Windows.Forms.MenuItem -ArgumentList "Exit"

$menuItemEnable.Checked = $True
$menuItemEnable.add_Click({
	$menuItemEnable.Checked = !$menuItemEnable.Checked
	If ($menuItemEnable.Checked) {
		$ste::SetThreadExecutionState($ES_CONTINUOUS -bor $ES_DISPLAY_REQUIRED)
	} Else {
		$ste::SetThreadExecutionState($ES_CONTINUOUS)
	}
})

$menuItemExit.add_Click({
	$notifyIcon.Dispose()
	[void][System.Windows.Forms.Application]::Exit()
})

[void]$contextMenu.MenuItems.Add($menuItemEnable)
[void]$contextMenu.MenuItems.Add($menuItemExit)

$notifyIcon = New-Object System.Windows.Forms.NotifyIcon
$notifyIcon.Icon = [System.IconExtractor]::Extract("imageres.dll", 96, $False)
$notifyIcon.Text = "Prevent Sleep"
$notifyIcon.ContextMenu = $contextMenu
$notifyIcon.Visible = $True

$ste::SetThreadExecutionState($ES_CONTINUOUS -bor $ES_DISPLAY_REQUIRED)

[void][System.Windows.Forms.Application]::Run()