When trying to activate Windows XP or Windows Vista system by using online product activation service provided by Microsoft, Windows Product Activation (WPA) wizard will reject the license serial or product key entered by saying the activation key is invalid or has been entered incorrectly. Then a pop up window appears asking user to re-enter the product key or activate using automatic phone system. Even … Continue reading Unable to Activate Windows XP and Vista with COA OEM Key Online Without Phone Activation