How to see previews of old quicktime movies (old codec)
Not sure about the Finder preview function. You would have to find a preview handler written for that specific codec (whatever it might be) and compatible with Yosemite. A bit of searching might find that, if it even exists.

If all you want to do is play the video try VLC at videolan.org it's free and well supported and will not try and covert it, just play it as is.