Screenshots
As a consequence of hardware overlay use, a screenshot program (for example, the one automatically built into Windows that activates when a user presses the PrtSc key) often does not capture the content appearing in the hardware overlay window. Rather, a blank region containing only the special mask color is captured. This is because the screen capture routine doesn't consider the special video memory regions dedicated to overlays - it simply captures the shared main screen as rendered by the software's graphical subsystem. Some Digital Rights Management schemes use hardware overlay to display protected content on the screen, taking advantage of this quirk to prevent the copying of protected documents by way of screen capture. Disabling the support for overlays causes the normal overlay-using software to fallback to the shared memory, thus enabling screenshot capture.
Read more about this topic: Hardware Overlay