BackTrack is the most top rated linux live distribution focused on penetration testing. With no installation whatsoever, the analysis platform is started directly from the CD-Rom and is fully accessible within minutes.
It’s evolved from the merge of the two wide spread distributions –Whax and Auditor Security Collection. By joining forces and replacing these distributions, BackTrack has gained massive popularity and was voted in 2006 as the #1 Security Live Distribution by insecure.org. Security professionals as well as new-comers are using BackTrack as their favorite toolset all over the globe.
(the above link tells more on backtrack and the title link goes to the how to crack page)