You continue on with the instructions:
"Rename the com.camerabits.PhotoMechanic folder by adding -old to the name. If there are any com.camerabits.PhotoMechanic.plist files, then you can delete them or add "-old" to their names. There could be 3 of these plus 3 copies ending with Lockfile. Close the Finder window.
Start Photo Mechanic. It might complain about the registration. If it does and you do not have your registration info handy, then quit Photo Mechanic. Go back to the Library folder and then the Preferences folder. ( Library folder shortcut will be in the left sidebar of any Finder window ).
Photo Mechanic should have created a new com.camerabits.PhotoMechanic folder. Open the com.camerabits.PhotoMechanic-old folder and move the com.camerabits.PhotoMechanic.registration file to the new com.camerabits.PhotoMechanic folder.
Now Photo Mechanic should be reset so it looks as if it has just been installed for the first time. Try the same workflow to make sure Photo Mechanic is working correctly now. If not, then I recommend re-installing the Photo Mechanic application.
If Photo Mechanic is working correctly now, go to the Preferences and click the Import button. Locate the PM-old-prefs.PMX file from where you saved it earlier and Open it. When the list opens click the Import button to continue. Click the Yes button in the alert dialog to complete the Import. Photo Mechanic will need to quit to save the changes."
-Kirk