Philip:
Your question is very legitimate and it deserves a legitimate answer.
Versions of Windows 8 may seem complicated but they are quite simple if explained cogently and in some detail.
There are several ways to buy Windows 8. But first let me explain that Microsoft has a variety of promotion offers currently which are expiring soon. These range from a cheap upgrade for Windows 7 users who bought after June 2012 to on line downloads for $39.95 to Beta user upgrades, to factory installed W8 on new computers to, W* upgrades from W8 regular to W8 PRO to upgrades from previous such as Vista and XO, to upgrades from W8 factory regular install to W8 Pro, to Builders license.
It seems that after January 31, 2013 you can forget about the cheap, advantageous come on pricing. Windows 8 will sell for $199.
To answer your question succinctly I will have to say that based on my experience and observations that a W8 download on line for $39.95 is a serious mistake. I have read about many problems. Normally you have only one or two options in stores such as Costco, Best Buy, Staples. Windows 8 PRO upgrade from a previous version such as W7, Vista, XP, 98. Or W8 upgrade from W8 regular *( factory installed ) to Windows PRO. For normal use Windows 8 is quite adequate. Win 8 PRO contains much encryption and other features not normally interesting to the home user. *( You can't buy W8 regular. It only comes pre-loaded with new computers ).
So to boil it down your best bet, if a home casual user, and no professional business, is to buy the Windows 8 Pro version *( upgrade from previous version ) at you local supplier such as Costco $66.95, Best Buy, Staples $69.95 or to go on line and order from such as CompUSA or several others soon to beat the price increase.
Check out your system requirements to be sure you can run it.
