Click Slide Show > Set Up Show.
Under Show type, select Browsed at a kiosk.
This will disable all keys except Esc, and mouse click.

If you ONLY want the slide to advance on the click of an action button (and
not eg with the space bar or other keys) then you have to use kiosk mode. The
disadvantage is that on click animations will no longer work.

There's a workaround for this here:
http://www.pptalchemy.co.uk/powerpoint_hints_and_tips_tutorials.html#animation