i cant connect my pc to my tv?

i have a hitachi L42vp01u. it has been connected to my pc and was working fine. one day i decided to mess about with the display settings on my pc and now when i try to connect it to my tv is says out of range and pc not connected after the inital start up screen which can be seen fine. i have tried using safe mode but this is also showing a blank screen saying out of range. my pc is workin fine on a 19 inch moniter. can any one help please??