doubt you'll find something good for free without going the illegal route, just do what I said and be done with it. You could have been downloading photoshop by now...
Gimp. It's the closest thing to photoshop you will find for free. It's not the easiest program to use but neither is photoshop. There are a ton of tutorials out there so if you are serious, download gimp (google it) and then take a look at some tutorials before diving in. It can be quite intimidating.
Oh and it's AN editing program, not A editing. There is an "n" added to "a" if the next word has a vowel sound at the beginning of the word.
Examples:
a dog
an elephant
an hour (note vowel sound)
a dollar
an inn (similar to when I used it in the sentence)