I have really messed up my monitor's horizontal & vertical and all the rest of it. It is so cockeyed and not very square. It does not fit my 17" monitor very evenly...if this makes any sense.

I have been working on it all evening, and I don't know how to fix it. Does anyone know how I can get all the proportions straightened out? Is there a website or somewhere where it tells what the proportions should be for a 17" monitor...like what the numbers should be? Thanks