According to information posted Monday and Wednesday by Alex Kochis, a licensing manager on the WGA team, virtually all of the 60 million PCs worldwide that failed WGA's validation tool are indeed violating Microsoft's licensing policy in one way or another. Kochis posted his comments on his blog on the Microsoft Developers Network.

Most of the reports of "false positives" by WGA "were due to data entry errors that were quickly corrected and only occurred for a short period of time," Kochis wrote. He said only a "fraction of a percent" of those 60 million copies of Windows XP deemed illegal have turned out to be genuine.

Given the number of Windows XP users, a fraction of a percent could still mean hundreds of thousands of genuine copies of Windows may have been incorrectly deemed to be pirated. Contacted separately, a Microsoft spokeswoman declined to elaborate on that figure.

Since April, when Microsoft escalated its WGA program by having the scanning tool stealthily install itself onto many PCs, the antipiracy tool has been the subject of numerous complaints from users claiming that their legal copies of Windows failed to pass WGA.

According to Kochis, about 1 in 5 of the 300 million copies of Windows XP that have been scanned by Microsoft's WGA tool fail to pass.