Ive got a Smart playlist with the following parameters:
File Path, Starts with, D:\Movie Path (This is the path on my hdd)
Duration, Is Less than, 2.10
Duration, Is Greater than, 1.30

Its set to video only, list 3 items and order by random shuffle.

This gives me a random movie of 'medium' length. (If there's a better way to do this I don't know what - ideally instead of the file path I Would be able to say Library path starts with - so the playlist wouldn't need to know where these files are on the the HDD - which would be much better)

Anyhoo with the list as above, if I remove a file from the folder (Using windows explorer) mezzmo doesn't seem to realize this - and its still feeding files that don't exist to my media streamer - or at least the file-names. When I try to play one of them of course the WD box says it cannot play the file.

Its probably worth noting also that the folders in question are also present in my library - as folders added to a playlist.