Millions of Windows users may unwittingly be test subjects for an unfinished Microsoft antipiracy tool.The software maker has been delivering a prerelease version of Windows Genuine Advantage Notifications software to PCs as a "high priority" item in the built-in update feature in Windows. The tool, also known as WGA Notifications, is used to validate the authenticity of Windows software installed on a PC. The move is a first for the software maker. Microsoft normally asks people to join test programs before it initiates the download of any such trial software. "I don't think that we have done it before," David...