Microsoft are in quite a bit of trouble with regard to their supposed "unhackable" OS activation malware in Vista, with Charlie over at the Inquirer just recently having briefed us all on a brute force cracking mechanism which works in such a way that it just continuously tries different key combinations until it comes across one that Vista sees as being an actual unique and fully legitimate key.
Might not seem like such a big deal until you learn of the severe damage it may end up causing down the track.
NGOHQ explain how it works in more detail here.
It is a simple brute force attack, dumb as a rock that just tries keys. If it gets one, you manually have to check it and try activation. Is is ugly, takes hours, is far from point and click, but it is said to work. I don't have any Vista installs because of the anti-user licensing so I have not tested it personally.
The method of attack has got to be quite troubling for MS on many grounds. The crack is a glorified guesser, and with the speed of modern PCs and the number of outstanding keys, the 25-digit serials are within range. The biggest problem for MS? If this gets widespread, and I hope it will, people will start activating legit keys that are owned by other people.