How does installing a new version of Mac OS X work?
March 13th, 2010 | 
Author: I want to buy the new version of Mac OS X when it releases, but wanted to know a few things:
1. Does installing a new OS erase my Hard Drive?
2. When I install the new OS, will it erase the old OS from my system?
3. Is an Operating System stored on the Hard Drive?
PLEASE HELP.
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Installing or upgrading to a new version of Mac OS does not erase your hard drive. If you select erase and install your hard drive will format and your data will be wiped. When you install a new OS, you are doing an upgrade. Additional and new features are added to your actual installed OS, and making it up to date with the latest features of the new OS. Yes, an operating system is stored on the hard drive. From my experience I upgraded my mac two times. From Mac os x 10.2 to 10.3 to 10.4, and I never had a problem.
1. Yes.
2. If you partition your hard drive, you can have 2 "hard drives" that you can use. But partitioning causes you to have to erase it anyway.
3. Yes.
You probably won’t be able to run Leopard AND Snow Leopard (I am assuming you have Leopard, it’s the same with Tiger) unless you have the install discs for both OSs.