simple question, does anyone knpw a good application that allows you to create or alter a 3d image?

The best thing i know of close to that is Blender(http://www.blender.org/), but i haven't used it enough to learn how it really works. Takes a lot of computer power though, so if you've got something with 1GB or less of RAM, and a generally old computer, its gonna be slow for you.

This is the program I use and I LOVE it. you can make water sims, soft bodies, games, animations, particle animations, and pretty much anything you want. It will be frustrating to use at first, but you will learn to love it. (for help and tutorials just check out youtube.com)

U can give 3dsmax a try to. It's used by alot well known gaming companies, for example the makers of the grand theft auto series

Wings 3D is worth a look. Best thing about it - it's a free download. Some of the work I've seen produced on it is pretty amazing tbh.