Display help needed..

I just upgraded my video card from an integrated Intel x4500 to a hd4650. It works fine but i noticed that on the bottom and top of the screen (Im using a 19 inch tv as monitor) there are black lines that I cant fill out. Ive tried different resolutions but i still cant fill them out ( with the integrated card I could fill them) and when i watch movies on vlc the black lines on bottom and top are bigger (i played with the settings on vlc for video ie. aspect, zoom etc..) The integrated card could play movies full screen. am i doing anything wrong? thank you very much