To unlock the vault on the second floor of the Centennial building you must collect the projector slides from Room 200 and then play them in the video archive room (Room 207) to reveal the code (IX-VI-I). If you then turn the dials on the vault to the indicated number it will become unlocked: Dial 1: IX, Dial 2: VI, Dial 3: I.
Useless Trickets Achievement (Digging up the Past Sidequest)
Added 23 Apr 2012, ID #8340
The video below shows you the location of ALL the dig sites to complete the 'Digging up the Past' sidequest. The sidequest can only be done on a second playthrough of the game and you will need a shovel. Completing this sidequest also lets you get the special Ending E - 'Surprise!'. A map of Silent Hill can be found on a table just before you exit Devil's Pit (before you enter Silent Hill).
When you return to the thief's apartment after you have completed the quest 'Stolen Goods' there will be a pile of discarded clothing where the thief's corpse was hanging. Press A on the clothing pile to switch between Murphy's standard outfit and a black hoodie with jeans.
At the diner near the begining of the game there is a cash register behind the bar area. If you take the coins out of it and place them in the jukebox in the corner of the room the very first Silent Hill theme will play.
Henry Townshend's Apartment from Silent Hill 4: The Room
Added 16 Mar 2012, ID #8275
To reach Henry's apartment go to Landsdale Ave. Between Brite St. And Cook St. And look for two bright windows with a reachable ladder from above which can be pulled down. When you climb up the ladder and enter the room, you will notice that it looks almost the same as in Silent Hill 4 but with a few differences.