This old G5 of mine will be getting its first-ever OS reinstall in the next week or so, and it will be somewhat uncharted territory for me. I am finally going to take the plunge with Leopard, but I want to keep Tiger just in case the new cat and I don't get along. My main concern is how to best allot drive space for the two OSes*. Putting OS X and OS 9 on the same machine was easy, since OS 9 took up a fairly small and predictable amount of space. Given that Leopard and Tiger apparently need separate versions of many apps and utes, however, I do not feel comfortable putting one or the other on a small partition and crossing fingers that I never run out of room. On the other hand, I do not want to wind up with lots of wasted, difficult-to-use space, and I want to avoid cumulative file redundancy wherever possible. I don't really use OS X's built-in folders to store my documents, and all my applications currently live in the global apps folder as opposed to my Home folder. A few specific questions: What's the best way to keep personal OS settings and info (mail, bookmarks, etc.) synchronized across both OSes? if I update Adobe CS3 to run with Leopard, will it still function on Tiger? or will I need two copies of everything? Is putting both OSes on the same partition doable? If so, is it a good idea? Is Leopard ready for prime time yet? It sounded pretty awful at first, but I'm way past due taking the leap (whether it becomes my daily-use OS is another story) So, anyone have any sage advice on the matter? Would be much appreciated. *The internal drive setup will likely be 1TB for the main drive and 400GB for the secondary.