Re: Windows 7 isn't easy to purchase anymore, if at all.
Whether you can still purchase Windows 7 depends on your relationship to Microsoft.
If you are an ordinary customer, it is now *impossible* to buy Windows 7 in accordance with the strict Microsoft terms and conditions, unless you come across a supplier who has remaining stock of retail licenses.
If you are a Business Associate, there are a number of things that Microsoft will allow you to do to ship Windows 7.
Many system builders (like Dell) bought Windows 7 OEM licenses upfront (remember all those stories about MS claiming that Win 7 had a fast uptake rate because of counting these pre-purchases as shipped systems), so have a stock of licenses they can use to put on newly built machines. As I understand it, MS are no longer allowing OEM Win 7 licenses to be purchased, so they will run out at some point.
One of the interesting options is that Microsoft allow what is called a Refurbished Machine license. These are mainly for companies in the corporate refurbishing business, who can install Win 7 on systems originally sold with Win XP or Vista before selling them on. There are some suppliers who sell these licenses on to end-users or small businesses, possibly against MS's business guidelines. But I have seen at least one missive from MS that they tend to turn a blind eye to this practice.
So while it is still possible to get Win 7, it's becoming increasingly more difficult as time goes by!