Help! there are no monsters in my game!

[Jereth8]

Ive played through the game before and KNOW when and where monsters should be.
This playthrough there are no monsters, just sound effects, I go through the water level, no monster! I'm jumping around in the water and it never shows up to kill me, Prison level still nothing. What's wrong with my game, also, I cant change my settings, no matter what I do, I cant get it out of full screen or change anything else. help.