I managed to replace the hard drive in my PowerBook with a Hitatchi Travelstar 7200 RPM, 80 GB drive. The instructions from www.pbfixit.com were excellent as well as their screw guide which I used to dutifully place and tape all the screws I removed. The drive is now formatted and appears to work. I still have to wait until tomorrow morning to get my backup and restore it. I completely understand the warning “no user serviceable parts inside”. Replacing a hard drive in a laptop takes time and patience.