Okay I don't think it can be be more specific beyond major version for Windows unless some sort of scripting is done and then the sample is highly subjective. All the User agent string contains is: Windows NT 5.0 - 2000 Windows NT 5.1 - XP Windows NT 5.2 - Server 2003 Windows NT 6.0 - Vista Windows NT 6.1 - Windows 7 Kris