I have a 21 inch imac with a dual core 3.6 Ghz processor 8 GB of ram and a Radeon HD 5670 graphics card. i want to play a game on my computer and surf the web on the tv i have it connected to but when i load a game in full screen mode it shuts off the other monitor. Ive looked at the system preferences and cant find anything. is there something i can do about it??