The Final Cut Pro package contains an inbox notice describing how to register QuickTime Pro, however the information provided does not specifically state where the information is to be entered in QuickTime 4 Pro.

To register the version of QuickTime 4 Pro that comes with Final Cut Pro 1.2, enter the words "QuickTime 4 Pro" in the "Registered to" field. Then enter the serial number included on the sheet in the appropriate field within QuickTime 4 Pro and continue.