A Ruler for Windows, as the name suggests this program brings for you an on-screen pixel ruler.
    Compatible with your Windows 7, Vista, XP and 2000; this free program displays a very useful virtual ruler on your Windows screen. You are provided with the option to choose a rich wood-grain ruler, or a clear see-through plastic ruler which can be launched with the touch of a button. This is a very useful application especially while layering one or more rulers over your work. The clear plastic ruler also allows you to continue your typing under it. This ruler can be flipped horizontally or vertically, resized to an exact length or resized by dragging it to a comfortable length. One can also place ticks on preferred edges and click the ticks to automatically draw a measuring line. This useful ruler can be used on as many computers as you would like.
    This free to use ruler also supports the 2x, 3x, and 4x modes to take snapshots of the whole screen and magnify it for measuring between very fine points.