Once upon a time L0phtcrack was the premiere password cracking tool. Then Symantec took hold of it via their acquisition of @stake and soon put the tool into moth balls.
In January the developers (formerly of The L0pht) acquired the source code, upgraded the tool, and announced its re-release at the SOURCE Boston conference.
The new version supports 64-bit Windows and has upgraded rainbow tables that help makes cracking passwords much quicker.
As a password testing tool it's pretty good stuff. But, if you simply need to recover a lost Administrator password then there are certainly much easier and faster ways.
L0phtcrack 6 is reportedly going to be sold for prices starting at $295 an upwards to $1195.