That should not have had any effect on your screen resolution. You should be able to change that by right-clicking on your desktop, going to the "Settings" tab, and adjusting the slider bar. Please provide the makes and models of your motherboard, graphics card, monitor.
ye i already tryed.. but wierd thing is that the gpu thinks that its another monitor. before the resolution just went to 1440x900, now its going to 1600x1200 and every single screen resolution is there, but not 1440x900