Windows Genuine Advantage is an anti-piracy tool loathed by many, tolerated by some, and even appreciated by others. How you feel about it may depend in part on whether or not you've been caught in its snares: the "authentic software" validation tool is known to have falsely identified thousands of "pirated" Vista installs.

As Microsoft steps up its war against piracy, the company has decided to slightly nuance Windows Genuine Advantage (WGA). Rather than identify users as either in the clear or not, the company has added a third classification for users who set off some, but not all of WGA's undisclosed piracy-detection functionality. Users will now find that Windows XP installs are labeled as genuine, non-genuine or "not sure."

While Microsoft has not responded to requests for comment, it's quite obvious what is going on here: Microsoft has added "not sure" as a way of cutting down on the number of false positives associated with WGA. As many as one in five PCs were failing WGA checks, but this new setting should both reduce this and give Microsoft the chance to investigate further the kinds of things that are landing folks in the "not sure" category.