The buttons on my “developer” Core 2 Duo likewise started disintegrating. I decided to tear away the remaining rubber on that side & cleaned everything up a bit. I then found that small pieces cut from a matchstick were just the right size to sit inside the (former) rubber button depression & to press the button on the PCB. A small dab of hotglue both held the matchstick button in place & sealed around it (although, I would not want to depend upon is “waterproofness”) !!