Mute sound in Windows using Keyboard?

I do not know of any ways to do this. Perhaps you should buy a keyboard which includes a mute button and volume control - many do.

If your goal is to avoid using the mouse, you can access the sound volume control from Start > Run > sndvol32.exe or create a shortcut to it on your desktop and assign a shortcut key to it. But this would only get you as far as the volume control - you'd have to tab down to the mute button and spacebar it to mute it.

There may be a much simpler way, but this is all I could think of.