...this in the other thread you posted in, cos I didn't see this one! 9.1 is an important part of OSX, because you need it to run Classic apps. Pre-installed X boxes tend to have X and 9.1 installed on the same partition, I think (mine did). It's just a case of choosing a different system folder to start up from under 'Startup Disk'. I think you'll find there are plenty of people here who don't find X is quite ready for it to be their primary OS yet. But whatever, i totally recommend having a play and making up your own mind before you decide against using X full-time.