For the record, my experience of WGA is as follows:
I've never actually *seen* WGA complain about a hardware change; the only times I've ever seen it are when reinstalling on exactly the same hardware (eg 3 times in a row because of a problem with slipstreaming drivers).
In principal though, if you change more than a few items of hardware at once (obviously this would include transplanting the disk into another machine) or whenever you reinstall then Windows will ask to be reactivated. If you reactivate too many times over a short period, it will demand that you call the phone number to use automated phone activation. At some point it will escalate to non-automated phone activation where you actually speak to a person. This is the furthest I've ever seen it go, though I believe there's a further level where you speak to the person and you have to give them a plausible reason for why you've installed the same copy of Windows two dozen times in the last week. If you then can't persuade them, this would be the point where you have to pay for a new license.
This is obnoxious and hateful, to be sure, but it is entirely unlike the behaviour described. The half-truths and outright untruths directed at Windows from some parts of the open source community make it hard to maintain credibility when describing legitimate grievances or technical problems, and this undermines us all.