BootCamp ControlPanel->Online Keyboard: F14 for me on Mac Alum Keyboard. Unlike Mac this does not create Png to desktop, but is saved to Clipboard where Windows Accessory "Paint" can be used to "Paste" (from Clipboard), "Edit" if you wish, and "Save" (to desktop).
Attached Pic (double click to see bigger) has taskbar PasteScr icon of display with paint brush on it which is my shortcut to mickey mouse script that copies clipboard to desktop. So after F14, PasteScr puts Jpg to Desktop.
More and Script here. I got it from "The Scripting Guys" at Microsoft.