My lcd monitor no longer works properly so I had to purchase a new one. I went with an LED tv and am now using an hdmi cable. I made it my primary monitor that now shows the desktop. I then disconnected the old one. It works fine until I turn the computer off. When I restart, the tower just beeps at me and won't start using the tv as monitor. I have to plug in the old one then restart, very annoying!! What am I missing?