Video Thumbnails Not Always Shown

Looking for advice or assistance regarding thumbnail display in Vista-64
environment. Currently have about 200 short video files that are mostly
MPG format, but some AVI and MOV. In all cases, I may or may not get a
thumbnail display of the file. In other words, some MPG file will show
the thumbnail, while other MPG files will not. (same case for other
formats). I would like to see the thumbnails for ALL files. All image
files (jpg, bmp, etc) display thumbnails fine.

In most cases the files were created with the same device, so there is
no logical reason for seeing the thumbnail for one file and not the
other. All files play fine in the appropriate players, although similar
issues occur in the player preview pane.

I've tried clearing the thumbnail cache, making sure Show Icons not
checked, etc, etc. I checked properties for the files and found no
differences other than date/time info. I've read a hundred post - but
don't see the same problem anywhere else. H E L P.
Thanks in advance.


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deckstein