There should be a button too, but it's simple to add a line so that it also defaults to any provided preference.

By "free windows" do you just mean an unactivated copy of Windows? That doesn't prevent the user from configuring their preference in the browser itself.

… is that even legal to do for microsoft? Are there no requirements to adhere to certain standards? Would have thought that is part of it.

what would the requirement be? "thou must provide the full paid service to those who do not pay"?

That's fine, too. Either way, give the user the choice.