I have a Powerbook 667 with 512 Ram. I am also running OS X 10.1.5. During processes (Like burning a CD or encoding MP3's in iTunes) or even just scrolling through documents in Microsoft Word or surfing the internet, my computer just goes to sleep intermitantly and randomly. It may do this twice in a 2 hour session so it is not all of time. However, it is harmful depending on what process you are running. I have the energy preferences set to "Never" for all of the sleep options. Is it hardware or software? I am totally stumped. Please respond, please!!!!