blender can be downloaded for linux, windows, (and maybe even macs...) , it is free so there is no problem with me linking to it, as raylin said. I use winXP also, just download the .zip version of it.

I have created some pretty cool stuff with it, animated rockets, (i started making a dragon), I used it to make graphics for a game I made, a ring, and a hovertank, to name a few

its a pretty full-featured program, like i said.