Need a simple way to remove 1/3 of the right side of a Mp4 video

Hi.

This is my first time using this forum. I recently took a video using my Canon HD Camcorder, which I have converted into MP4 format. The issue is that I need to remove about 1/3 of the right side of the video in order to get rid of images that I do not want. Is there anyway to do this simply?

Thanks in advance.

Andrew