From searching on the web, it appears the movies generated by the Pentax are MPEG-4, but you said the extension is mov (as opposed to mp4), so I guess they’re in a QuickTime container. Normally QuickTime 6 should be able to handle this. To be sure, open the file in QuickTime, click on Movie, then choose Movie Properties. On the left drop-down menu choose Video Track and on the right drop-down menu choose Format. What does it say on the Data Format line?
If it’s MPEG-4, then I’m really puzzled that it won’t play. I guess at that point you can try downloading 3ivx (at http://www.3ivx.com) and see if the file plays in Windows Media Player.