Changing video format

My daughter used her digital camera to record various little videos of her friends last year at college. When she would download the videos into her laptop, they would automatically be in Quicktime format. Now she has been playing around with the Windows Movie Maker program and would like to use some of these video files from her camera. She says it isn't working because the files were downloaded in the Quicktime format and the Windows Movie Maker format won't recognize it. Is there a way to change the format of these files so she can use them? Thanks in advance for any advice.