How to edit out a specific noise in a video?

I always wondered how they do it on shows like Planet Earth (for instance I assume they somehow edit out the sound of the helicopter blades during an areal shot as you can still hear the ambiance and whatnot.) I have a Nikon D3100 and without the option of having an external mic the built in mic pics up the auto focus motor AND the sound of the lens when I zoom in and out and it's just so frustrating. If anyone knows if this is possible and what software to use to do this, please, let me know!

You can use one of the following software:
Free Video Editer:
Windows Movie Maker (for windows) http://download.live.com/moviemaker/
iMovie (for mac) http://www.apple.com/...fe/imovie/

Professional Video Editer:
AVS Video Editor (for windows) http://www.avs-video-editor.org/
Final Cut Pro (for mac) http://www.apple.com/...cutstudio/
Adobe Premiere (for windows) http://www.adobe.com/.../premiere/
Sony Vegas Pro (for windows) http://www.sonycreativesoftware.com/vegaspro