If you've got hard disk problems on your Mac, I highly recommend Alsoft's DiskWarrior. Yes, Symantec's Norton Disk Doctor (part of Norton Utilities) used to be tops, but in the last few years, DiskWarrior has proven to be the safest and most effective. In general, though, you should try Apple's Disk First Aid (OS 9 or earlier) or Disk Utility (OS X) first, then DiskWarrior, and then Norton Disk Doctor or Micromat's Drive 10. (A good friend and Mac guru, Patrick Yeung, initially passed on this sound advice.)

I was able to quickly fix 2 disks today using DiskWarrior. One was an removable 3.5" MO (Magneto Optical) disk and the other was an internal hard disk. The MO disk wasn't recognized by Mac OS 9 and so everytime we inserted it, the system asked whether the disk should be initialized or ejected. I had to run DiskWarrior first (and have it as the active application) and then insert the MO disk so that DiskWarrior was able to "see" it (without the system interrupting first). On the second disk, we were not able to delete any folder located on the desktop; the system would say that the folder was locked. I tried using Norton Disk Editor to unlock the folders (unticking the Finder Locked checkbox) but the changes were not sticking. In both cases, DiskWarrior fixed the disks in about 5 to 10 minutes. The whole process is pretty much automated — you just click a few buttons and disk problems are gone!