Recupera la Product Key di Office via PowerShell (testato su Windows 10 e Microsoft Office 2016 ProPlus), vedi https://wp.me/pdQ5q-9dx

OfcProductKey.ps1

function Get-MSOfficeProductKey {
    param(
    [string[]]$computerName = "."
    )

    $product = @()
    $hklm = 2147483650
    $path = "SOFTWARE\Microsoft\Office"

    foreach ($computer in $computerName) {

        $wmi = [WMIClass]"\\$computer\root\default:stdRegProv"

        $subkeys1 = $wmi.EnumKey($hklm,$path)
        foreach ($subkey1 in $subkeys1.snames) {
            $subkeys2 = $wmi.EnumKey($hklm,"$path\$subkey1")
            foreach ($subkey2 in $subkeys2.snames) {
                $subkeys3 = $wmi.EnumKey($hklm,"$path\$subkey1\$subkey2")
                foreach ($subkey3 in $subkeys3.snames) {
                    $subkeys4 = $wmi.EnumValues($hklm,"$path\$subkey1\$subkey2\$subkey3")
                    foreach ($subkey4 in $subkeys4.snames) {
                        if ($subkey4 -eq "digitalproductid") {
                            $temp = "" | select ComputerName,ProductName,ProductKey
                            $temp.ComputerName = $computer
                            $productName = $wmi.GetStringValue($hklm,"$path\$subkey1\$subkey2\$subkey3","productname")
                            $temp.ProductName = $productName.sValue

                            $data = $wmi.GetBinaryValue($hklm,"$path\$subkey1\$subkey2\$subkey3","digitalproductid")
                            $valueData = ($data.uValue)[52..66]

                            # decrypt base24 encoded binary data 
                            $productKey = ""
                            $chars = "BCDFGHJKMPQRTVWXY2346789"
                            for ($i = 24; $i -ge 0; $i--) { 
                                $r = 0 
                                for ($j = 14; $j -ge 0; $j--) { 
                                    $r = ($r * 256) -bxor $valueData[$j] 
                                    $valueData[$j] = [math]::Truncate($r / 24)
                                    $r = $r % 24 
                                } 
                                $productKey = $chars[$r] + $productKey 
                                if (($i % 5) -eq 0 -and $i -ne 0) { 
                                    $productKey = "-" + $productKey 
                                } 
                            } 
                            $temp.ProductKey = $productKey
                            $product += $temp
                        }
                    }
                }
            }
        }
    }
    $product
}

Get-MSOfficeProductKey