At the main menu, select "Password" and the game will prompt you to enter a 4 letter password on the typewriter for unlockables.

Password Effect

HINT Hints (Unlockable 7)
BIKE Jukebox (Unlockable 6)
ROSE Movies (Unlockable 5)
LEET Unlockable 2
CARS Unlockable 4
GONG Visuals 02 (Unlockable 3)
AAAA What is a password? (Unlockable 1)

The Japanese version of the game contains 20 passwords to unlock.

Password Effect

HINT Hints (Unlockable 20)
NRJQ Jake Hunter Quiz (Unlockable 2)
BOXJ Jukebox (Unlockable 12)
NONE Mini-Case Extra 01 (Unlockable 14)
ENGI Mini-Case Extra 02 (Unlockable 15)
BORO Mini-Case Extra 03 (Unlockable 16)
HIGE Mini-Case Extra 04 (Unlockable 17)
STOP Mini-Case Extra 05 (Unlockable 18)
NANT Mini-Case Short Story (Unlockable 19)
HANA Movie Viewer (Unlockable 9)
SFCE Staff Comment 1 (Unlockable 4)
PRSD Staff Comment 2 (Unlockable 6)
MINU Taiba's Extra Story (Unlockable 13)
OTSB Unused Character Designs (Unlockable 10)
YASA Visuals 01 (Unlockable 3)
BUTU Visuals 02 (Unlockable 5)
CARS Visuals 03 (Unlockable 7)
MVCL Visuals 04 (Unlockable 8)
PAPA Visuals 05 (Unlockable 11)
AAAA What's a password? (Unlockable 1)