You could help a bit reducing the size of the image holding down the "alt" then pressing once the "print screen" button, this will capture only the active window (so no task bar etc).
after your alt-print screen, as stated above, open mspaint, (or ms word or anything that could hold your pictures) and do a ctrl-v, this will paste the picture , do not forget to save before closing the mspaint.
Good luck.
Ps: the "print screen" is a keyboard button you'll find left of the "Scroll Lock" button, in the right half of the keyboard.
Then On Your Key Board Press " Prt sc " That Copys The Screen The Go To Paint Anything That Can Hold Your Picture. Then "Ctrl" "v" And The Same Time Into The Paint