Without a description of the actual problem I would suggest you set the video resolution of the 2nd display in your dell video control panel to match the native resolution of the Sharp TV.
TVs usually overscan the desktop when used with a computer. This is so when watching TV you don't get blanks. Since TV programs don't use the edges of the screen there are no problems. With a computer there are buttons at the edges that get lost.
Some TVs do have a way to turn of the overscan. Check the TV manual. Some video drivers offer controls to compensate for overscan.