This thread should be a reminder to BACKUP all your data before you upgrade to Leopard. A friend of mine and me had serious problems when we did the upgrade on different systems (a macbook and a mac mini). In both cases we had those fatal problems: 1. Leopard installer started up, and asked where leopard should be installed 2. After selecting the disk, the installer informed me, that leopard could not be installed on the disk and that a new partition must be created 3. Obviously, I didn't do that and tried to reboot tiger: The reboot did not work, tiger couldn't boot anymore. 4. Booted up with the install CDs and checked the disk with disk utility: Didn't work: It reports that the catalog is damaged I was lucky to have a complete backup. My friend didn't... Now he hopes to get back the data by some other means. I dont't have any idea why this was happening. I had a lot of applications on my macbook: maybe one of them caused the problem. Don't know about the state of the mac mini of my friend. Did anybody else have those problems? It is a serious issue and if others had is as well, apple should know about that.