I need mac os leopard or os x 10.5 where can I purchase this from.

Hi, by download, do you really mean you tried to install it from a DVD?

Where exactly are you seeing this needs 10.5 at?

Even the oldest 2007 MacBook can run 10.6...

http://www.everymac.com/systems/apple/macbook/specs/macbook-core-2-duo-2.0-white -13-mid-2007-specs.html

Snow Leopard/10.6.x Requirements...

General requirements

* Mac computer with an Intel processor

* 1GB of memory (I say 4GB at least, more if you can afford it)

* 5GB of available disk space (I say 30GB at least)

* DVD drive for installation

* Some features require a compatible Internet service provider; fees may apply.

* Some features require Apple’s MobileMe service; fees and terms apply.

You will have to look on eBay or Amazon fo a vlack retail Leopard install disk. It may cost up to $200.

The OS 10.6 Snow Leopard install DVD is available for $19.99 from the Apple Store:

http://store.apple.com/us/product/MC573/mac-os-x-106-snow-leopard

Note, if you have any pre-2006 applications, these will not operate once you upgrade to 10.7 or later.