I think it's alt+printscreen for the active window, and some computers you have to hold shift+printscreen. Or on my laptop, it's the function key-printscreen.
If you are wanting a pic, easy way it to open paint and right click on the white bit and select paste, then save as whatever you want to save it as.
D'oh, you are right, I was thinking alt and typed shift.....gotta love it when my heart starts its BS...I can't hold a thought to save my life (even worse than normal!) when that happens... Like a blonde on steroids!