Under Defeat Codes -

Wallpaper:
Insert the game disc in a PC CD-ROM drive to find game-themed wallpaper.

Weapons gallery:
Successfully complete the game.

Bonus Graphics gallery:
Successfully complete the game two times.

Additional continues:
Accumulate the indicated amount of cumulative game time to unlock the corresponding number of continues.

0:00:00 to 0:59:59: 2 continues
1:00:00 to 1:59:59: 3 continues
2:00:00 to 2:59:59: 4 continues
3:00:00 to 3:59:59: 5 continues
4:00:00 to 4:59:59: 6 continues
5:00:00 to 5:59:59: 7 continues
6:00:00 to 6:59:59: 8 continues
7:00:00 to 7:59:59: 9 Continues
8:00:00 or more: Unlimited continues