HELP ME PLEASE !!!

I USE GFORCE 4 AND I USE NVIEW 2 & BSPLAYER

ONCE I COULD VIEW FULL SCREEN ONLY ON T.V AND SOMEONE

COULD STILL WORK ON THE COMPUTER REGULAR,

BUT NOW I CAN'T !!!!!! I HAVE TO DO FULL SCREEN ON THE

COMPUTER TO SEE FULL SCREEN ON T.V

I TRY EVERYTHING AS IT WAS !!!!

WHAT COULD BE THE PROBLEM ??????????????????

THANK'S EVERYONE