How long can I use Windows without activation?

A simple answer is that you can use it forever, but in the long term, some of the features will be disabled. Gone are those days when Microsoft forced consumers to buy a license and kept rebooting the computer every two hours if they ran out of grace period for activation.

Is it legal to use Windows without activation?

2 Answers. Hi, Installing Windows without a license is not illegal, activating it through other means without an officially purchased product key is illegal.