It looks like Microsoft has an upcoming "feature" that can kill your OS. They're going to require you to use the "Windows Genuine Advantage" software - some of the most laughably named software ever - which checks back with Redmond periodically so they can check your license and what applications you have installed to check for unregistered software. And if you don't install it within 30 days or prevent it from "checking in" with Redmond, Windows will activate a "kill switch" and cease to function completely. What's the "genuine advantage" for customers, exactly?
Considering Microsoft's inability to make software that works properly and securely, the chances of either (a) WGA failing to install properly and block the kill switch, or (b) a malicious worm or virus taking advantage of this "feature" seem rather high.