I concur with Picasa. Free, good, and lots of features if you want to investigate them. The way it describes its features is a bit intimidating, but the basic premise is it will never harm your original image, so you can experiment a bit. You should try Picasa simply to know what you can do for free.
paint.NET is a good, free, photo editor.
Irfanview is a good, free, simple to understand photo viewer.
I'm sure one or more of the above will fit your needs.