Full scree option will not stay on

i have tried to find a solution for this but no luck. i have a 2 year old dell vostro 200 duel core e4500 w/ 2.2 ghz and 2.00gb. running windows xp-medial player 10 and adobe player 10. streaming movie sites allow for full screen play but i cannot get this option to stay. full screen will stay on about a minute and then revert back to the small screen. i have disabled the screen saver and set display times to not interfere w/ movie play. this is really irritating since i am sending this to my hdtv. no one i know has this problem. it is probably just a setting i need to adjust. thanks in advance for any suggestions.

i had heard of this but did not know what to do about it. will try this weekend and let you know if it works. thanks so much for the response. you were the only one with a suggestion.