Return windows product key

Get-WinProductKey.ps1

function Get-WinProductKey {    
    $map="BCDFGHJKMPQRTVWXY2346789" 
    $value = (get-itemproperty "HKLM:\SOFTWARE\Microsoft\Windows NT\CurrentVersion").digitalproductid[0x34..0x42]  
    $ProductKey = ""  
    for ($i = 24; $i -ge 0; $i--) { 
      $r = 0 
      for ($j = 14; $j -ge 0; $j--) { 
        $r = ($r * 256) -bxor $value[$j] 
        $value[$j] = [math]::Floor([double]($r/24)) 
        $r = $r % 24 
      } 
      $ProductKey = $map[$r] + $ProductKey 
      if (($i % 5) -eq 0 -and $i -ne 0) { 
        $ProductKey = "-" + $ProductKey 
      } 
    } 
    $ProductKey
}

# http://powershell.com/cs/blogs/tips/archive/2012/04/30/getting-windows-product-key.aspx