Windows default thumbnails can become boring over time, especially if you watch videos on your computer frequently. Fortunately, you can customize thumbnails for your videos in Windows Media Player. Customizing has the added benefit of keeping your playlists organized and searchable.
Launch Windows Media Player.
Click on the little down-arrow under the "Library" button. Select "Video." You should see a list of all the videos that are stored on your computer.
Right-click on the video you want to edit and select "Advanced Tag Editor."
Click on the "Pictures" tab on the Advanced Tag Editor and hit the "Add" button.
Browse through your pictures and select the one you want to use as your thumbnail. Acceptable file formats are .jpeg, .gif and .bmp. Make your selection and click on "Open." Hit "OK."
If you cannot find the Advanced Tag Editor in Step 3, right-click on the file and select "Properties." Make sure the check box titled "Read-only" is unchecked.