This is how to delete the Final Cut Pro preferences:

 

Quit Final Cut Pro.

 

on your MAC internal hard drive, navigate to

/users/yourloginname/library/preferences, and delete this file -

com.apple.FinalCutPro.plist

 

navigate to

/user/yourloginname/library/preferences/FinalCutProUserData

and delete these three files -

Final Cut Pro 6.0 Preferences

Final Cut Pro Obj Cache

Final Cut Pro Prof Cache

 

thats is !  Relaunch Final Cut Pro, and you will be "starting from scratch".

on OS X 10.8 Mountain Lion, to trash your preferences - 

on the Mac, click on Go

hold the Option key down, and you will see "Library" appear - click on Library

scroll down to the Preference folder

in the Preferences folder, delete this file

com.apple.FinalCutPro.plist

in the same Preferences folder, scroll down to the FinalCutProUserData folder

and delete these three files - 

Final Cut Pro 7 Preferences

Final Cut Pro Obj Cache

Final Cut Pro Prof Cache

that's it !  Relaunch Final Cut Pro, and you will be starting from scratch.