Well, Jerry, it looks like others have already given you the same answer I would.
I think Adobe Photoshop is the ultimate photo-editing software these days, and has been for quite some time. I started with the LE (Limited Edition) version that came bundled with my flatbed scanner way back when. Eventually I shelled out the big bucks for the pro version when I started a photo restoration business. After a year I decided that was too much work for too little return, but I sure as heck learned to use Photoshop.
I notice there's a free trial version listed at the top of <A target="_blank" HREF=http://www.adobe.com/support/downloads/product.jsp?product=39&platform=Windows>this page</A> on Adobe's website -- 41 megabytes worth /w3tcompact/icons/shocked.gif. You have to sign up as a member (free) and you'll obviously need a high-speed connection. Might be easier to find someone who has one of the bundled versions.
There may be other good software out there, but since I came across Photoshop early on, I never looked too hard for anything else.
One word of warning about Photoshop -- be prepared to embark on an enormous learning curve. I have years of experience with it and have collected 5 books to help me along, but I freely admit that I'm still kind of a mid-level user.
If you don't get documentation with it (depending on how you get it), I highly recommend starting with
Photoshop Visual Quickstart Guide by Peachpit Press. Easy reading, lots o' pictures and screen shots.