I was able to download the new ISO X64 Professional Windows 10 software this morning. The following test was run on a Dell E6500 Laptop. Install the ISO and skipped the Product Key to start. Windows 10 loaded and completed successfully. Restarted the laptop and it asked for a Product Key, gave it the Windows 10 Professional KMS Client key which started with W269N.. ended with ..T83GX. Windows 10 didn't like the Product Key because there was no KMS Client on the new Dell install. Loaded up my old version of KMS 2.5.1 and executed a Windows Client Activation. It accepted the Windows 10 Product Key and activated the new system. I then ran the Microsoft License Manager, and it shows that the KMS 2.5.1 with the Product Key from Windows 10 Professional is a legitimate key. Hope this information helps some others.