It's called a Memory Leak or a Ram Overdrive, it's when the computer is running to many program or have a very high tech PC with a low power-unit cooling the computer.
Because of that, you'll often have 'freezes' when the sounds makes a fuck up sounds and the screen changes into odd colors.
Because of that, you'll wants to stay awa from FPS unless you get a new power unit or found out what is the cause of the leak.
If you keep playing it, the computer will crash and will nee to be repaired that is how my Window 7 PC died.