I was having a little bit of trouble with my Mac Mini locking up and being unresponsive. Of course, the answer I got from Apple support was to back everything up, format the drive and reinstall OS X. Because that sounded too much like a Windoze solution, and I had read the article Resuscitate an unconscious Mac; I tried the solutions in that article and nothing worked.
Then I read the section again about trying a utility like DiskWarrior. What could it hurt? I was faced with reinstalling the OS and all the applications and restoring my data from the backup that ran all night after I was able to bring the Mini up in target mode, so I ran off to CompUSA and picked up a copy.
An hour later, my Mini was repaired and back in business.
I can recommend this utility if you’re facing the same dead Mac issue.