Last modified: 2014-05-15 12:58:19 UTC
http://stats.wikimedia.org/wikimedia/squids/SquidReportOperatingSystems.htm For April 2014: "NT 5.0 = Windows 2000, NT 5.1/5.2 = XP + Server 2003, NT 6.0 = VISTA + Server 2008, NT 6.1 = Windows 7." reported by Gene Conner
I added newer releases in the explanatory notes.