所谓全屏幕显示，是不是就是让客户区占据在全屏幕的范围？如果不是，那么是怎么做到的？
另外，如果是使客户区全屏幕，那么如何使窗口盖住桌面的任务栏？
[解决办法]
call this api
LONG ChangeDisplaySettings(
LPDEVMODE lpDevMode, // graphics mode
DWORD dwflags // graphics mode options
);
for fullscreen mode, dwflags=CDS_FULLSCREEN
ensure that the DEVMODE structure passed to ChangeDisplaySettings is valid and contains only values supported by the display driver
return value:
DISP_CHANGE_SUCCESSFUL
if failed, call GetLastError() to get return code
