Did you really like an older version of iMovie? (Or any older version of any product Apple created you have the install disks for?) Use a product called Pacifist (can be found in the links section) and get your old copy back. WARNING: You will have to rename or move whatever packages you are installing! i.e. iMovie .app will overwrite the newer iMovie if it exists in Applications. For example:I dragged the iMovie 11 app to the desktop and will put it back later after I rename the “old” iMovie 6.
The upgrade even works! There are (2) upgrades for iMovie 6 so running the upgrader twice.