Also, salespeople tend to sell towards the clients capabilities. So if you walk up and admit that you do not know much about the subject matter they will "dumb down" and sell you the older technology. Why? Other than being rather "bubbly" the Luna interface of Windows XP was more evolution than revolution. So the salesperson is banking that you'd be more familiar with the basics of XP and not require much overhead in the form of technical support may it be from walking in asking questions or calling in via telephone.