After press the prntscr or CTRL+prntscr, the screenshot goes to your PAM automatically. U should goto MS Paint, MS word or any other graphic editors and Press CTRL+V immediately, then save the image…If not you caouldnot get the screenshot…
if u wanna capture anything on the screen, perhaps this key can't help u. Im using PCHand Screen Capture, it could help u capture any screenshot on the screen. i think it is pretty good, i know it from my friend, u can also try it. Hope it could help.
http://www.screen-capture-record.com/