The great open source Nipper tool, used for auditing infrastructure and network devices, has now become commercial. So visiting http://sourceforge.net/projects/nipper/ would give you the latest version (1.0) which is of little help, as it contains the stripped version. So, no use of it. Fortunately, my friends on Null suggested me few links from where still the older version (0.11-12) could be downloaded. One of such link is:
http://tools.l0t3k.net/NETWORKutils/ , you can download nipper-inone-0.12.6.zip. It's an exe and you can run it directly.
Alternate method: Upgrade to BackTrack5 R2. The latest version includes the Nipper-ng tool. To update to the latest version: http://www.backtrack-linux.org/backtrack/upgrading-to-backtrack-5-r2/
Also, once upgraded you need to install Nipper on the new kernel:
apt-get install nipper-ng
Screenshot from BT5 R2: