Newest Version of Nmap is available in GUI called Zenmap.
On December 13, 2007 , insecure.org has made the announcement of the availability of the newest version of Nmap , which is Nmap 4.50 . Since Nmap is the most powerful network scanner tool which is more capable to be run under Linux Environment , insecure.org seems to want it to be run under Windows in its best performance too. That’s why Zenmap has been developed by insecure.org. Zenmap is the combination between Nmap command line tool and GUI which will simply offer the ease of use of its features to Windows users. The recently released version 4.5 has more features , such as : 2nd Generation OS Detection, the Nmap Scripting Engine, a rewritten host discovery system, performance optimization, advanced traceroute functionality, TCP and IP options support, and nearly 1,500 new version detection signatures.
Windows Installation manual
Download Zenmap - Windows Version