Thumbnails for video files are not showing in Windows 7

I had the same problem. Just found this link about Media Preview, installed it and worked perfectly. My thumbnails are back:

http://www.snapfiles.com/get/mediapreview.html

Media Preview enables Windows Explorer to display video thumbnails for just about any video format out there. If you are seeing blank or generic thumbnails for some of your video files, just install Media Preview and select the formats you want activate. The next time you open your video folder, it will display thumbnails for all your movies.

I managed to fix this. The problem was that my registry entry was modified incorrectly by some software.

The HKEY_CLASSES_ROOT\.mp4\ShellEx entries were modified. I changed them to this:

[HKEY_CLASSES_ROOT\.mp4\ShellEx]


[HKEY_CLASSES_ROOT\.mp4\ShellEx\{BB2E617C-0920-11D1-9A0B-00C04FC2D6C1}]
@="{c5a40261-cd64-4ccf-84cb-c394da41d590}"


[HKEY_CLASSES_ROOT\.mp4\ShellEx\{e357fccd-a995-4576-b01f-234630154e96}]
@="{9DBD2C50-62AD-11D0-B806-00C04FD706EC}"

merged it and restarted my PC.

I fixed this changing the settings of K-lite codec pack:

1. From start menu choose All Programs.
2. Click K-lite Codec Pack folder.
3. Click Codec Tweak Tools folder.
4. Open All options.
5. Click Thumbnail Settings.
6. Select the file types for which you would like to display thumbnails or click Select Windows default.
7. Click Apply & Close.
8. Restart the computer for this changes to take effect.