Excellent guide which gave me the confidence to give it a try - unlike the YouTube videos which range from comical to plain scary. I didn't have a thin enough T10 screwdriver but managed OK using one with a flat blade which I magnetised first. Only problem came when I tried to install Snow Leopard. When I tried to format my new 1Tb drive Disk Utility said the drive was 7.3 Tb and refused to format the disk, citing input/output errors. I assumed that I had screwed up somewhere and went through the whole process again, only to get the same result. I decided to install the OS to an external drive as a temporary measure and found that the disk was then correctly recognised. After that, everything was plain sailing. If you aren't too sure, give it a try and save some money. Just be painstaking and patient. I'm a Silver Surfer so with no IT skills to speak of. If I can do it, so can you. Many thanks.