Quick Time Player?

I recently purchased some instructional CD-ROMs that use Quick Time Video. I decided to use an old Dell laptop (sorry don't have specs. right now) to play videos. I want to be able to keep the wife from nagging that I am on the Home PC too much. I am having issues with the video playing. They have a sputtering like motion. The sound and video are as best as I can discribe; chattery. Is this a lack of memory or processor speed on this laptop? Can I convert these videos to play in Windows Media Player?