You do not need to Activate Windows 10 to install it, but this is how you can activate later

[Windows Central]

Microsoft has done an interesting thing with Windows 10. Besides giving it as a free upgrade to anyone with an activated Windows 7 or Windows 8 PC the OS is also one big shareware demo.

Specifically, by the demo I mean near fully functional OS that you can install anywhere to try out. This ability means you can download the Windows 10 ISO right from Microsoft and install it on a home-built PC, or any PC for that matter. Even Mac users can do this and install the OS using Bootcamp (more on this later).

Full story from the WindowsCentral blog...