I have a number of folders with video clips in them, in .avi, .mp4, and .mov formats.

With each of these there is an associated .thm file which I assume to be a thumbnail image generated by Windows. In fact, I recall having been able to view these images. I think that they may have appeared as the icon for each file rather than being viewed separately. But now they have been associated with an application that shows them as its icon next to the one for the video file, rather than showing a thumbnail. (First application that hijacked the files apparently was OpenOffice, but I've tried other associations and still have the same problem.)

How do I recover the ability to view these thumbnails in Windows Explorer?

I am also not being allowed to rotate JPEG images unless I make a copy of them.

Is the problem with file associations or maybe with System Properties performance settings? I've just turned all of these back on for maximum appearance -- this show thumbnails for .JPGs but not for the videos. Maybe I have to restart the computer?

Or the problem may be that I created the folders on a different computer with a different login, and stored them on an external hard drive. Even though I am logged in as an administrator, Vista may be unahappy with that.