Those who are not very good at math are probably going "what the hell?" at about this point so let me clear up a few details.
first off you need a hex editing program like Hex Workshop
Now let me explain to you what he was talking about with "reversing the vlaues". Open up the calculator in windows click View then scientific.
Now type in the width of your desired resolution and then click the hex button. For this example lets say you want 1440 x 900
you get 5A0 which as a pair is 05 A0
then you reverse the values: A0 05
same goes for 900
384 which is 03 84 which you will enter as 84 03.
NOW all the directions should make perfect sense.