To open a secret chest, hold down <ALT>-<RIGHT SHIFT>-<~>
 from the overhead view.
 
 From here, you get a chest you must enter a code for.
 
 Each chapter has a different code, here they are:
 
 1. 6478
 2. 9216
 3. 7702
 4. 2132
 5. 5052
 6. 0680
 7. 0194
 8. 4743
 9. 9995
 
 From Steven Wirsz, Fido 1:250/108