Ok,  I this is something random I thought of while feeling lazy, that I think windows does not have and that it maybe was worth posting about...  This however could be useful for disabled people too :
So the WAY my computer is positioned is out of reach to me..  I often SWITCH between using headphones and speakers while using my computer and I thought it WOULD be nice if I could leave my headphones in it's socket and be able to switch between which I want to use, at a click of the MOUSE (instead of pulling the jack out or in to switch between).

I use XP, but I'm not sure if it's already possible with XP? or any windows versions.   But like I say, I just thought it would be something to ask about here and maybe it's something very basic that could be there, that doesn't seem to be there?In Master volume for example.I have never had the need to do what you seek. However it appears that your operating system is XP. If that is so it seems that by PLUGGING in your speakers to either front or back and then plugging in your headset to the alternative remaining you will obtain sound from both. If you then desired to limit to only one or the other from volume control you can mute that which you desire to cancel. Here is a source that seems to confirm that.
http://www.pcreview.co.uk/forums/getting-sound-speakers-headphones-plugged-t2420635.html
truenorth