Hi there cazxx if you right click your mouse then from the menu click on properties,when you are in properties at the top select settings and you will see a little slider thingy that says resolution slide this down with your curser to a lower pixel level and press apply if the icons and righting are to your sattisfaction press ok if not try again.
Just one more thing to ad here if you have personlised wallpaper then this might change to just a plain backround and you will have to set your wallpaper back again, also the icons might move places on your screen so you will have to move them again... Hope this helps.