Need software update

OS X 10.5.8 is the highest you can go with an update.

In order to go higher you must purchase the Snow Leopard install DVD by calling Apple for it.

Allan

Upgrading to Mountain Lion

You can upgrade to Mountain Lion from Lion or directly from Snow Leopard. Mountain Lion can be downloaded from the Mac App Store for $19.99. To access the App Store you must have Snow Leopard 10.6.6 or later installed.

If you need to purchase Snow Leopard contact Customer Service: Contacting Apple for support and service. The price is $29.00 plus tax. You will receive physical media - DVD - by mail.

Third-party sources for Snow Leopard are:

Snow Leopard from Amazon.com

Snow Leopard from eBay

After you install Snow Leopard you will have to download and install the Mac OS X 10.6.8 Update Combo v1.1 to update Snow Leopard to 10.6.8 and give you access to the App Store.

If you need to purchase Lion contact Customer Service: Contacting Apple for support and service. The cost is $19.99 (as it was before) plus tax. It's a download.

Be sure your computer meets the minimum requirements:

Apple - OS X Mountain Lion - Read the technical specifications.

Macs that can be upgraded to OS X Mountain Lion

1. iMac (Mid 2007 or newer)
2. MacBook (Late 2008 Aluminum, or Early 2009 or newer)
3. MacBook Pro (Mid/Late 2007 or newer)
4. MacBook Air (Late 2008 or newer)
5. Mac mini (Early 2009 or newer)
6. Mac Pro (Early 2008 or newer)
7. Xserve (Early 2009)

Are my applications compatible?

See App Compatibility Table - RoaringApps - App compatibility and feature support for OS X & iOS.

Am I eligible for the free upgrade?

See Apple - Free OS X Mountain Lion upgrade Program.

For a complete How-To introduction from Apple see Apple - Upgrade your Mac to OS X Mountain Lion.

You want to upgrade not update. If you want 10.6.8, you need to purchase the disc directly from Apple Sales by calling them. If you want update further, follow Kappy's instructions.