Secret
First highlight the extra new game option.
Then press the following keys: W, W, S, S, Q, E, Q, E, Escape, Enter.

This only works if you haven't changed your key configurations, otherwise you'll have to find out the right buttons yourself.Now just choose the difficulty and the riddle level. You should hear Heather's sigh when you start the game and when you see Douglas he'll be wearing boxers and no pants

UFO ending:
Successfully complete game and unlock the Princess Heart costume and the Heather Beam weapon. The Heather Beam is a special weapon which you can only use if Heather or Cheryl is not holding any weapon. Defeat all monsters and Bosses using only the Heather Beam. Note: The "Monster defeated" counter should read 0 kills.

Possessed ending:
Kill all monsters with any weapon except melee ones, preferably the unlimited sub machine gun (a special weapon).

Extra interactive scenes:
To get extra scenes while playing the game, use a memory card with at least one finished saved game file from Silent Hill 2. New interactions with some objects and new scenes will now be available. These scenes are similar or with some type of reference to the previous game. For example, Heather trying to look for something stuck into the toilet in the mall.