I would, go to an Apple store or call them, and ask them why your iMovie is not working with your video format.
It may just be something simple to tweak.
I have a Mac and well, we make movies on it all the time.
As the other poster said: I would, get another Camcorder, that CAN be used with iMovie.
Many Camcorders are cheap.
Even the "Flip" camcorder etc. Or using an iPhone for example.
Getting video editing software for the Windows PC, versus getting a different camcorder, will be a big price difference.
And, (my husband used to do movies/editing on a PC ), it is a real pain in the butt doing it on a PC. Doing it via iMovie on a MAC is MUCH MUCH easier and not at all time consuming.
iMovie is SO easy.
It is worth it, it is already on your Mac, and if you just get a different camcorder that is compatible with iMovie, for a good price, it will all be worth it in terms of time/effort/ease/results and enjoyment.