Chirie

I want to sell videos on my site, but instead of downloading them, I want users to be able to reproduce them on-site, once bought. So, when I add a virtual product and it asks me for the number of downloads of the associated file, I would like to input -1 (0 is for unlimited) and make it not downloadable. Can you tell me which files I need to edit in order to do this? I guess I'll have to override the Admin Products controller and then edit the Product page template, but I want to be sure. Thanks.