How do I get rid of the high pitched whine in from my cameras mic?

[Kazaskater]

I have a picsio HD camera, and the video quality is great, but the audio sucks. it has a high pitched whine and its really annoying. Is there any way I can kinda mask it or make it go away? I have a mac with imovie, or I have windows in case I need to download any programs. I can get the audio off the camera alone, then change it somehow, and put it back. I just dont know how to change it. any ideas.