If I were you, I'd keep the system you have. You're probably going to notice a slowdown going to OSX on your machine, even though you have dual processors. The fact that you have an older system bus, graphics card, hard drive and memory limits will inhibit your OSX experience. That's not to say it won't work, but if what you've got now is stable and doing what you need, then don't change it. If you want to check out OSX (which is great) for other purposes, then you can install it without it messing up your current OS9 system and see how it performs with general tasks before trying out PT. My guess is that you'll find it a little lagging in responsiveness though, so you'll be best in OS9. I'd look at upgrading to OS 9.2.2 though, and the latest version of PT that runs on it for your hardware - 9.2.2 was extremely stable, and the versions of PT that run on it offer some significant improvements over 5.1. Slim