How do I get a screen capture in Windows on MacBook?

I'm a new guy to Mac/Mountain Lion, but not to computers, so this question may be a bit dicey.

I have used Gadwin PrintScreen for years on Microsoft Machines. During Setup, I am allowed to use Ctrl+Printscreen but now I am using, only occasionally, Windows 7 x64 on a partition on my MacBook Pro/Retina. Considering that there is no Printscreen key on the keyboard, I can no longer use the configuration I am accustomed to in the Windows environment on my lovely, shiny Mac. Only combinations ofCtrl/Alt and F keys are allowed. I get "Can't use that key. Already assigned to, etc."

So then, my query is this, on the Windows side, what keyboard combo will allow me to get a full screen capture? I've tried everything and combed the Apple community to no avail. If there is no keyboard combination, what app can I use that will allow me to do so in a Windows environment on a MacBook Pro/Retina. Just a month old.

I know how to execute this on the Mountain Lion side, but that key combination doesn't cut it on the Windows side.

In closing, I hope the solution is an app download to allow me to choose a configuration.

Thanks for reading,

Kelly J.