Select the video file you want to compress, when it is highlighted the file has to show the extension if it doesn't show dont worry, go to the 'tools' menu which is found on the top of any window, click on the 'folder options' there appears the folder options window, here you can see few pages, select 'view' there uncheck the option 'hide extensions for known filetypes'.
(tools> folder options>view>uncheck hide extensions for known file types)
Now change the extension for the video file you want to zip as txt.(e.g suppose the file is "filename.mpeg"
change the extension to 'txt' now the file is "filename.txt". After changing the extension now use the zipper software to compress the file now you can see a great decrease in the size of the file.
When you want to play the file then extract it and don't forget to change the extension to 'mpeg'.