I have so many problems in a day..

Alright so 3 weeks ago i ordered a KVM switch off eBay from Hong Kong yadyad...
( KVM switch lets you switch between multiple computers or computer / xbox with a button and will display on one screen, like multiple inputs on a tv...) Any ways everything is good xbox runs 1680 x 1050 like it should yayay, boot up pc... what's this it will not work in 1680 x 1050... says it can go to 1920 x 1400 or something any ways my screen res is way under what it can handle, so im like WTF so i Google some stuff, possible solutions and nothing is working... Which makes no sense because my xbox is running right now in 1680 x 1050 and also currently running my pc... not in 1680 x 1050 is has to be in 1600 x 1200 which only displays have my screen or 1400 x 900 which is horrible... Anyone know the solution. ?