notepad

function Get-WindowsKey {
  ## function to retrieve the Windows Product Key from any PC
  ## by Jakob Bindslet (jakob@bindslet.dk)
  param ($targets = ".")
  $hklm = 2147483650
  $regPath = "Software\Microsoft\Windows NT\CurrentVersion"
  $regValue = "DigitalProductId"
  Foreach ($target in $targets) {
    $productKey = $null
    $win32os = $null
    $wmi = [WMIClass]"\\$target\root\default:stdRegProv"
    $data = $wmi.GetBinaryValue($hklm,$regPath,$regValue)
    $binArray = ($data.uValue)[52..66]
    $charsArray = "B","C","D","F","G","H","J","K","M","P","Q",
          "R","T","V","W","X","Y","2","3","4","6","7","8","9"
    ## decrypt base24 encoded binary data
    For ($i = 24; $i -ge 0; $i--) {
      $k = 0
      For ($j = 14; $j -ge 0; $j--) {
        $k = $k * 256 -bxor $binArray[$j]
        $binArray[$j] = [math]::truncate($k / 24)
        $k = $k % 24
      }
      $productKey = $charsArray[$k] + $productKey
      If (($i % 5 -eq 0) -and ($i -ne 0)) {
        $productKey = "-" + $productKey
      }
    }
    $win32os = Get-WmiObject Win32_OperatingSystem -computer $target
    $obj = New-Object Object
    $obj | Add-Member Noteproperty Computer -value $target
    $obj | Add-Member Noteproperty Caption -value $win32os.Caption
    $obj | Add-Member Noteproperty CSDVersion -value $win32os.CSDVersion
    $obj | Add-Member Noteproperty OSArch -value $win32os.OSArchitecture
    $obj | Add-Member Noteproperty BuildNumber -value $win32os.BuildNumber
    $obj | Add-Member Noteproperty RegisteredTo -value $win32os.RegisteredUser
    $obj | Add-Member Noteproperty ProductID -value $win32os.SerialNumber
    $obj | Add-Member Noteproperty ProductKey -value $productkey
    $obj
  }
}

save as zzz.ps1

open powershell as admin

Set-ExecutionPolicy RemoteSigned

Import-Module C:\Users\xxxx\Desktop\zzz.ps1; Get-WindowsKey