I am temporarily using DevC++. I have some windows code here that seems correct in changing to fullscreen: DEVMODE devMode; memset(&devMode, 0, sizeof(DEVMODE)); devMode.dmSize = sizeof(DEVMODE); devMode.dmBitsPerPel = 32; devMode.dmPelsWidth = windowWidth; devMode.dmPelsHeight= windowHeight; devMode.dmFields = DM_PELSWIDTH | DM_PELSHEIGHT | DM_BITSPERPEL; if(ChangeDisplaySettings(&devMode, CDS_FULLSCREEN) != DISP_CHANGE_SUCCESSFUL) fullscreen = 0; Obviously I have fullscreen and windowWidth and windowHeight previously defined... but the peculiar thing is that when I compile, my compiler returns this error: 'CDS_FULLSCREEN' undeclared (first use in function) I checked MSDN and it appears I'm using the ChangeDisplaySettings() method correctly.. Does anyone see a problem?