Make certain that your Mac is compatible with whichever OS you plan to upgrade to.
For Lion (OS 10.7) or Mountain Lion (OS 10.8), you need to go to the online Apple Store to purchase and get info on how to download. From there you should be able to download and upgrade to the most current OS (currently OS 10.9 – Mavericks). Go to the Applications folder and open “App Store”.
Fast & Free shipping on many items Download Mac OS X Snow Leopard v10. If you wish to upgrade FROM Snow Leopard, make sure you are running OS 10.6.8. Get the best deals on Apple MacBook Mac OS X 10.6, Snow Leopard Laptops and find everything youll need to improve your home office setup at. Afterwards you can start up from your old OS or Snow Leopard by pressing OPTION key during startup. Alternatively, install Snow Leopard to a empty partition that has been formatted as Mac OS Extended (Journaled) with the GUID option. however, I recommend making a complete bootable backup before doing so in case something goes wrong during installation, such as power outage. Many people simply upgrade directly over the old OS installation. After installing, do Software Update (under the Apple Menu) to bring Snow Leopard up to OS 10.6.8. If your Mac does not have an optical drive, the DVD has instructions on doing a remote install from another Mac on the same network. Starting with 10.8 Mountain Lion, Apple extended that to n-2 to protect both 10.7 Lion and 10.6 Snow Leopard, most recently releasing Security Update 2013-004 for both operating systems in September 2013. Then purchase the Snow Leopard install DVD from the Apple Store. So, when Apple released Mac OS X 10.6.7 for Snow Leopard, the company also rolled out Security Update 2011-001 for 10.5 Leopard. (If the word “Intel” appears anywhere beside “Processor” you have an Intel-based Mac.) To find out go to Apple Menu and select “About This Mac”. Apple : Series B004FVWA8U : Hardware Platform Mac : Operating System Snow leopard 10.6 : Item Weight 7 pounds : Color White : Processor Brand Intel : Processor Count 2 : Computer Memory Type DDR2 SDRAM : Optical Drive Type DVD RW : Power Source Battery Powered : Batteries 1 Lithium ion batteries required. If you wish to upgrade TO Snow Leopard (OS 10.6), make sure you have an Intel-based Mac (Snow Leopard will not run on a PowerPC processor) with at least 1GB of memory and has Mac OS 10.5 or earlier.