just open the app and minimize to tray (if you want)
then when the window you want to take a screenshot is open, just press
Ctrl + Alt + T and it will automatically cut out the window and save it to a .png file you choose.
(its png because it is the best quality for small disk size)
Good bitmaps are like 1.0 mb, who want images that big
After it saves the image, it asks you if you want to open it in paint, so you can edit the image faster than having to browse for it and open it.
This is perfect for people who write tutorials
http://jakesoft.net/index.php?act=view&id=9