I know this is possible to do but wanted to know which application to use..

I have a bunch of movies in both .wmv and .mpg format at the moemnt, what im looking to do is create a thumbnail from each of the movies however, rather than creating a thumbnail from the opening frame of the clip im wanting the clip to 'play' for around 15 seconds before the snapshot is taken.

Anyone know a good software application that will do this?

Regards,

Lee