Most savvy users know it by now that in order to upgrade your Mac to Leopard, you need to have Tiger on it. If you don’t have Tiger on it, you need to upgrade your Mac to Tiger first.
What if your Mac is already running Tiger and the installer still doesn’t install and complains that you need to have Tiger installed first? This is the problem I ran into today. We have a fairly recent MacBook Pro running Tiger (10.4.11) . When we tried to upgrade it, the installation process stalls at checking for previous OS.
I found some articles on line about how to solve the upgrading problems. Before I followed the instructions on line to fix it, I decided to repair the disk volume and fix the disk permissions first. You can do both tasks by running the Disk Utility included in the Leopard upgrade DVD. The repairing volume did not find anything wrong about the disk, but the utility did find tons of problems with the permissions.
Guess what, once the permissions were fixed, I was able to restart the installer process and get the system upgraded to Leopard.