I have some free alternatives for you as well, if you would like.
For graphics, another option for you would be Paint.NET. I find it's a better program than GIMP which is just too frustrating to use, and you don't have to download a bunch of plugins to get it to do what you want.
For sound you might want to try Audacity. It's for editing, instead of creation, but you can layer existing sounds and add effects to make completely new sounds. I've layered thunder, dog barks and explosions to make gun sounds before. It's fun.
If you are doing 8-bit sound effects and music, nothing beats Dr.Petter's tools.
sfxr for sound effects
musagi for music