Vista plugs piracy hole
Microsoft is taking action to thwart a possible hole in its Vista anti-piracy measures.
Users of the new operating system have to register their software in order to activate it. If that doesn't happen within a set time the software will lock-down giving limited functions until it is officially registered. But pirates have reportedly used bits of previous beta releases to create a version of the software which doesn't need to be activated. Another workaround uses the method Microsoft uses for activating software for enterprise clients.
Microsoft describes the pirated versions as "frankenbuild" systems. It will use Windows Update to require the Frankenstein systems to do the validation check. Because they use the wrong key they will not pass the test.
Failing the test means your machine loses some functions, after thirty days if you do not produce a correct key you will only be able to use your default web browser for an hour. But you can still access you files by booting in Safe Mode.
There's more on Microsoft's Windows Genuine Advantage
marketing guff blog here. 
There is also a comment from a deeply irritated user annoyed that his computer told him it was running counterfeit software and requiring him to spend an hour on the phone to support getting another activation key.