It seems your video port/card adj. on its own to accept the new display. Provided you can view it, go to the setting and return them under the video properties within the system itself, not the monitor. -OR- use the video port/card own s/w(Nvida/ATI) to do this if available.
So I decided to hook my computer up to a plasma 37 inch screen and then after I was done with it I unplugged the tower from the tv to my regular 17inch Dell monitor. Unfortunately the screen image on the Dell looks bigger and somewhat stretched. I've tried pressing the auto adjust button on the monitor and going on the screen setting but nothing has seemed to work! Can someone please help me out over here?