Microsoft is confirming what downloaders have known since Thursday afternoon: Chunks of the NT 4.0 and Windows 2000 source code have leaked onto the Web. We hear Redmond is telling some analysts that about 15 percent of the Windows releases got out; but so far, there is no "official" statement from Redmond. Microsoft officials say they are more worried about the potential IP violations of the source breach than of the security ramifications. The FBI is reportedly involved in helping Microsoft try to find the source of the leak.