Video Editing

OK, I'm a moron so I'm and can't get Imovie to work. I have a video clip (avi) which I made on my digital camera. I want to cut out part of it and then save both pieces. One piece I can then share as is, and the other I want to then fix the orientation of.

Anyone know any good free software that I can use or know how to do this easily in Imovie. I do own a Mac, so please no software for the PC only. ^^;