Adam -

Here are two photo editors - both small and free. I use GIMP at work since the cheap bastards won't pay for Photoshop - it does all of the rudimentary PS tasks. Getpaint is higher rated in some of the freebie software websites. There are free plugin filters also. Either one will do the job you need.

http://www.getpaint.net/index.html
http://www.gimp.org/

Good luck.