Hello, I need to disable the mouse in a fullscreen application. ShowCursor only hides the cursor, but I want to disable it entirely because you can still move the mouse to the upper right corner and click to close the window. When using DirectInput for mouse input in exclusive mode it disables the mouse exactly the way I want it. Do you know how to do that?

You don't want to disable the mouse, you want to disable the system menu on your window - usually done by setting the window style to WS_POPUP. Even if you could disable the mouse completely, that'd totally screw up multiple-monitor systems.