Though this might sound harsh, I intend it to be constructive criticism. I went through these same problems myself.
1) We can see your room. That kind of destroys the illusion.
2) The camera movement was a good idea, but it was at such a low framerate and was so jerky that it looked quite bad. The rotation around the castle would have looked sweet if it had only been smoother. Use a higher framerate. If you're using Windows Movie Maker and can't do a higher framerate, PM me and I'll send you links to 5 free animation programs.
3) The parts where he jumps and throws the spear looked really bad with the stick holding him up. In one frame we could even see your hand. PM me and I can show you a free way to make an object appear to be hovering using a technique called masking
4) In each frame of some of the shots, your shadow appeared on the set. Since you moved, your shadow did also. This looks pretty bad, too. Adjust your lighting so that you don't cast shadows on your set.
I think that that is pretty much it. Have no fear, you have the potential to get a lot better. It just takes practice. If you have any questions, feel free to ask, and I'll do my best to help out.
EDIT: Yeah, sound would have been nice.