In the second board where you have pile a box up to get over the cliff do the following. Pick up the smallest rock possible. Try to throw it to knock down the box farthest left. if you hit it just right you should have knocked down a Bannell1 M1 Super 90.

In the small town, go behind the church and build a staircase against the outer wall with boxes.  Climb the staircase and walk to the left along the top of the wall.  Keep walking on the wall while keeping to the right and you'll eventually fall into a secret level.

To select a level, push [Ctrl] + [Shift] + Q + W. Then release W.

To activate cheats, unlock command-line window by pressing [Alt] + [F11]. Then enter one of the codes below.

Effect                            Code
Ameliorate wounded character      INVUL
Display location                  LOC
Highlight interactive objects     BONES
Increase gore                     GORE2
Slow motion                       BIONICWOMAN
Suspend dinosaurs                 DINOS
Teleport to important locations   TNEXT
Unlimited ammo                    WOO
View ending sequence              WIN