can someone help with my tv :)

hi all ive got a new toy to stream my laptop to the tv, trouble is that when it does this the picture is too big, their was a setting before where i could change hight and width of the screen but for the life of me i cannot find it.





could one of you fine people on here tell me where it is, ive looked it ati catalyst but with no joy but i have come across it before. after all it is christamas...