Print screen on windows bootcamp

Download and install "Input Remapper"
It is a keyboard driver that helps mac keyboards be more useful under Windows.
It works well for my MacBook Pro (fn-eject is mapped to print-screen), and I assume it will work for the MacBook as well.

Edit: Also, my favorite thing about it is mapping the little enter key on the bottom row of the keyboard to the right mouse button. I don't know whether the MB has that key, but if so, give it a try. Now I wish I could do the same thing when booted to OS X.