MBP and MacBook Air SWAP - Change of ownership

I recently swapped my 13" MBP for an 11" MacBook Air.

How can I change the ownership, so that I am officially the owner of the MacBook Air?

Also, the person that swapped with me, left his OS on it without reinstalling a clean install, so now I am not able to install any programs as I'm prompted for an administrator password which I do not know, and doubt that the previous owner would provide it for privacy reasons.

The solution is to do a clean install of OS X Leopard... but how is this done?

There is no optical drive on a MacBook Air, and I only know how to do OS installs using MBP's or iMac's, not Air's.

Also, the seller did not provide OS X Leopard to me on an optical disk or a USB key - Does the Air usually come with OS X Leopard in some type of media (DVD or USB Key etc). If so, I will have to enquire as to why this was not provided.

Advice would be appreciated.

Not a huge expense, but it sounds like you will have to buy the disk set for your air, and a USB drive as well. The disk set should have definitely been provided as a part of the sale, but the right way to do this is to give him the disks for your machine on condition that he give you the disks for the air.

Yes, you need to request the install media to do a clean install (or possible repairs now or later) and/or his password so that you can set up your own account as admin and delete his. There's no reason not to provide you with that password if the machine is auto logging into his account as you already have access to all the data he left on it.

Thanks for the replies so far.

If the original owner has lost or sold the original OS Leopard disc, and unable to provide, what are my other options?

OS X Lion is coming out soon, is there anyway to install Lion without needing Leopard?

When upgrading to Lion, is there a way to completely WIPE the previous Leopard OS, so that I end up with a completely fresh OS?

It is unlikely that the original Leopard OS disc will be provided, so I will need to think creatively about work arounds for this issue.