The videos require Quicktime which is a free download available from Apple Computer.
The latest types of video files are relatively small and show a good picture. But they require the latest version of software (QT7) and a moderately capable computer. In some cases I have included another version of the video which is compatible with more computers and older software.
Usually (unless the video is quite short) there will be a menu at the lower right that will let you jump right to the chapter markers in the video - very useful.
Normally you would just click on a video link to view it. However since some of the videos are large it may take a long time to see them. If you click the link and it is taking a long time, I have an alternative suggestion.
Right-click on the link (on Mac: control-click) and select "Save Linked File As" (or "Download Linked File", or similar) to get a copy of the video. Put the video on the desktop to make it convenient to find. While it is downloading, get a coffee or something. Then when the file has been downloaded you can open it and watch it.