To take a full size screenshot in Windows using Apple or Mac keyboard, press Command and F15 keys together and paste it in Paint or other graphics software.
Mac Equivalents of Windows Keys
Command key = Windows key
Option key = Alternate or Alt key in Windows
Control key = Control or Ctrl key in Windows
Delete key (on numeric row) = Backspace key in Windows
Delete key (next to End key) = Del or Delete key in Windows
Return key = Enter Key in Windows
Fn key (next to Home key) = Function or Fn key in Windows
Full Size Magic Keyboard For Apple or Mac
Older Apple or Mac Keyboard Wired via USB (Full Size including Numeric Keypad)
Notes 