Rumors of Microsoft's successor to Vista have been cropping up virtually since day one, and if this latest one is to be believed, it looks like one of the earliest may have been right on target after all. According to TG Daily, "several industry sources" are now saying that the a very early version of the so-called "Windows 7" OS has already shipped to "key partners," and that Microsoft is now eying the second half of 2009 for a release of the real deal. That's a slight revision from the most recent rumors, which had pegged the debut as late as 2010 or, more vaguely, sometime within the next three years. As if that wasn't enough, Microsoft's apparently also lined up the next two early versions to be released, with the so-called M2 build slated for April or May of this year, and the M3 release slated to drop sometime in the third quarter. Given recent history, however, it's probably not the best idea to start marking your calendars just yet.