So I'm wondering. Because OS X is now shipped via iTunes how it is possible to restore system when it crash? I recently had problem with my Kubuntu. It worked on Friday, I'm starting it on Saturday and...screen is black system is not responding. In modern notebooks there are always rescue disc so you can restore system to the manufactured state. Is it (and how) possible on iMac? And, if yes, can I restore it with Time Machine disc? Thank you for your replies.