How do I distinguish between Windows 2008 and Windows Vista using javascript?

Question

I need to detect the SO of the user in a web application (IE only). I am using the function BrowserDetect.OS from javascript, but it returns the same String ("Windows Vista") when called from Windows 2008 and Windows Vista, and I cannot distinguish the user SO. Is there a way to detect this difference?

http://msdn.microsoft.com/en-us/library/ms537503%28VS.85%29.aspx

Answer 1

Very similar question (but not exact dupe) here