Vista - Hot to Stop DVD's from being watchable, but not CD's from playing

I have a vista laptop that I want to disable DVD'd from being able to be
played on. Regular CD's should work but not DVD movies.

I had an idea to change the DMA settings to make it run very choppy, but I
cant figure out how to do it on the vista laptop.

I dont want it saying DVDs are not allowed, rather, that it just wont be
watchable (possibly due to choppiness, etc..). So uninstalling any DVD player
is not an option.


Any suggestions would be most appreciated.

Thanks