how can i update my computer from osx 10.5 to a lion

You first need to purchase 10.6 Snow Leopard, (and update it if the version is not 10.6.6 or higher), and then purchase Mountain Lion, (10.8.x) using the Mac App Store.

I don't think Lion, (10.7), is available still.

Make sure you back up your system so you can return to the older OS if you don't like it.

You'll need to purchase Snow Leopard 10.6 first. Then get to 10.6.8 so you can access the App Store to purchase Mountain Lion. However, read:

After upgrading to Snow Leopard, if your system will only go as high as Lion, a redemption code can be order by calling Apple.

Imp68 a redemption code is for an iTunes gift. Nothing to do with what the op is asking.

sig wrote:

Imp68 a redemption code is for an iTunes gift. Nothing to do with what the op is asking.

Sure it is. If the Macbook is not capable of running Mountain Lion, but can run Lion, the OP will need to call Apple to get the redemption code for Lion as you can't directly purchase Lion in the App Store.

My bad. You guys are correct. Not enough coffee yet. :-)