Well now it's not quite so simple
I went to download.com and typed in Ubuntu in the search window. At the top of the list was a PDF converter which I know I don't need. Next is a link to webcraller.com search, so I clicked on that and got a bewildering 9 pages of different places. So I clicked on one that takes me to http://www.ubuntu.com/download . The first thing I see there is a screen talking about replacing my OS. This is precisely what I do NOT want to do!
So would someone who's a little more articulate please provide something I can get started with including how to be absolutely certain that I don't mess up my hard drive, and where to go to download Ubuntu.