How do i download window 7 or 8 to my computer

Hi Gina, for Windows 7, I recently found this excellent source: http://www.microsoft.com/windows/buy/default.aspx. You can download upgrade OR full versions for decent prices, go figure. I didn't find reliable sites for Windows 8 and 9, however, as my time machine is out of order right now; perhaps you could ask again in 2012 or so? "I think there is a world market for maybe five computers.” (Thomas J. Watson, Sr.)