>Is there a function for calling just the volume control?
>

Not that I'm aware of that has a consistent, knowable .CPL file name that can be used to start it. There may be one for your soundcard; i don't know, but for an example of where there are multiple interdfaces available, the NT system I'm working on now has the normal display interface control apnel applet named "Desk.CPL", but since I have a Matrox display card installed, there's also a Matrox-specific one one called MGAPANEL.CPL available. I don't know what you or your users will have available to them, but MMSYS.CPL is always available to control the generic installed multimedia interfaces.

I strongly advise giving your users access to a Windows System related control panel function to handle system-wide decisions about things like speaker volume, color sets, font and the like; it's at best ill-mannered and in vollation of the basic concepts behind the Windows OS interfaces; it's your user's machine, and system preferences, and not behaving in accordance with their wishes as expressed through the OS common control settings makes your application not adhere to the stand behaviors regarding Windows interfaces.

You can always tell them to install the volume control to the system tray and have them access the volume from the system tray applet. I prefer on this system to install the SoundBlaster 128 mixer control to my system tray; it gives me a whole lot more control than the default volume control does. That's my decision to make - the box to my right has an SB Live! card in it, and I load up a completely different set fo controls as a toolbar to give me control of the 3D SoundBlaster Live capabilities. I'd be downright annoyed to have you go in and frob the settings I've made so that things are set up properly for my SB Live! when I watch Pulp Fiction this afternoon during my lunchbreak.