Hi everybody, I'm working on a simple application that draws an alpha-blended picture on the screen's Device Context every 2 secs, I want to refresh the screen contents before the drawing operation (To erase the drawn pic), I have used many many trick but unfortunately, the screen won't refresh correctly, some regions still keep portions of the drawn pic I'm really frustrated from this issue :( These are the sources codes I have used, I'm using C# SendMessage(HWND_BROADCAST, WM_SYSCOLORCHANGE, IntPtr.Zero, IntPtr.Zero); // wasted time in the refreshing process is enough to keep this. UpdateWindow(HWND_BROADCAST);// does not work at all! InvalidateRect(IntPtr.Zero,IntPtr.Zero,true); // the same goes here. SendMessage(HWND_BROADCAST, WM_PAINT, IntPtr.Zero, IntPtr.Zero); // pfffff ! SendMessage(HWND_BROADCAST, WM_SETTINGCHANGE, new IntPtr(SPI_SETNONCLIENTMETRICS), IntPtr.Zero); // trying to refresh the explorer, no resutl I used also EnumWindows and call back , very slow and does not fit my case. I wanna refresh the whole screen Help please! Regards Waleed