[ Screen Capture_ ]
To take a snapshot, press the Print Screen key on your keyboard. Its the one that is (usually) above Insert and to the right of F12.
Now, open your preferred image editing program (photoshop, ms paint etc..) and press Ctrl + V to paste.
If you are pasting it into MS Paint (Start > Programs > Accessories > Paint) then make sure you resize the white area to something really small before pasting.
Copying text or taking another screenshot will replace your previous one.