Displaying the multimedia properties dialog from the control panel is very easy with the following code; the secret is to know to call rundll32.
begin
// Audio
WinExec('rundll32 shell32.dll,Control_RunDLL MMSys.cpl,,0',SW_SHOW);
// Video
WinExec('rundll32 shell32.dll,Control_RunDLL MMSys.cpl,,1',SW_SHOW);
// Midi
WinExec('rundll32 shell32.dll,Control_RunDLL MMSys.cpl,,2',SW_SHOW);
// CD Music
WinExec('rundll32 shell32.dll,Control_RunDLL MMSys.cpl,,3',SW_SHOW);
end