Turns out that a few forums, couple guestbooks and some web pages (including one HOME PAGE) have hot links to some files on my tutorial site.
One of the linked files is a silly video I use as an example and it is rather large, and seems quite popular.
Last night I moved the full video to it's new location, and replaced the original file with a much smaller altered file using the same name. The video begins normally, but the background music has been replaced with a voice-over that says " THIS VIDEO IS STOLEN AND ENDS NOW!". Then goes BLACK, ending the transmission.
For a week, vistors to those pages will find a disabled video and the webmasters will get the point. Once I remove the file, they will just get a red x, but in the meantime, I will have my revenge on these thieves! And I can afford a bit of bandwidth for this venture.
Got the idea from one of the several threads that describe how to block certain sites from hot linking. One of the threads told how to make a replacement image. Thought it could be applied to other formats too! Thanks for the idea!