the one thing that i love about windows xp is that you can use control alt delete, and set the priority of some programs to low, and improve overall performance. sometimes, when i play a game, or something it's very choppy. why? because there's another process that eats up a lot of cpu. i don't need it to eat so much cpu and focus on the game that i'm currently playing, for example: when encoding in imovie, i want to set it's priority to lower than normal, and then go play a game like marble blast. it will take longer to encode, but experience is a lot better. how can i do this in MAC OSX?