Retrieving the Windows product key

If you look for your product key on a Windows Server 2008 R2, you probably retrieve a key like BBBBB-BBBBB-BBBBB-BBBBB-BBBBB. The real key can be decoded from the DigitalProductId registry value.

Save the following function to a PowerShell file and run it. It also works against remote computers by passing their names to the -targets parameter.

function Get-WindowsKey {
    ## function to retrieve the Windows Product Key from any PC
    param ($targets = ".")
    $hklm = 2147483650
    $regPath = "Software\Microsoft\Windows NT\CurrentVersion\DefaultProductKey"
    $regValue = "DigitalProductId"
    foreach ($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
    }
}

Get-WindowsKey

The output lists the computer name, OS version, build, registered owner, product ID and the decoded product key.