What a fantastic guide. I've never done anything like this, other than increasing RAM, but 2 hours later and I've got a new hard disc in place and operating. The added comments help clarify enormously. And the tips to use pots and cardboard press-in's for the screws were invaluable. True to form, stage 16/17 was the hardest bit (a plastic lollipop stick helped me) followed, bizarly, by getting the screws back into the battery compartment - two are still a bit squint, but the battery fitted so no matter. Thanks again ifixit!