are ther any hidden files associated with videos which have been downloaded from the internet?

Answer 1

Yes, there can be files with 2 extensions, like for example, a potentially dangerous .exe fle can be named as love.avi.exe which will just show up as love.avi to you, unless you have enebled the `show hidden files' option

Answer 2

As with pictures, there can be a thumbnail file that your computer automatically generates for previews.