Old version Cygwin installation, refer to following URL:
http://hpds.ee.ncku.edu.tw/~smallko/ns2/setup_en.htm
Packages such as "XFree-*" (XFree86-base)can not be found in new version Cygwin. One can refer to following URL:
1.http://wiki.nus.edu.sg/display/CBR/Install+NS-2+on+Cygwin
2.http://my-hertz.blogspot.com/2009/06/preparing-cygwin-for-ns2.html
I have all packages of Cygwin(version 1.5.25-15) installed on my computer as 1.
