Hi If you install any OS either it is Windows 1 and you want to use office as a free product you can use it free only for 3 days on trial basis and after that you will have to activate it. If you will not activate it after sometime your product will get into Reduce Functionality Mode . It means that your office product will not be fully functional. I can suggest you that if you want to use office you can go for a subscription and it will not be very expensive. You can subscribe it on Monthly basis and you can use a fully functional office suite. There are multiple office suites available with multiple offers. You can install some of them up to 5 devices including your mobile devices. You can follow Office 365 3 Home Personal and Business Editions - Microsoft Store s to know more about office subscriptions.