this required a little more force than I felt comfortable with at first.

I did this not just for upgrade but because G4 had been out of service for over 12mths due to what I believed was a faulty logic board. Attempted re-installs of OS (when I found the disc) suggested HDD failure so I ordered a 160Gb replacement from ebay for £40 and have just replaced original 30Gb HDD with a 160Gb following these instructions - I have no previous experience in this type of work but now have a working lap top with fully installed OS up and running and all at a total saving of at least £827 based on new MacBook prices!!!