Well, you could've used the forum search

1. When you click on the Monitor tab, if you've got the 'show incoming searches' box ticked, the top half of the screen shows a list of incoming searches that somehow relate to files that you're sharing. In the bottom part of the screen, you'll see a list of uploads in progress/completed (other users downloading your files)

If you want people to only be able to download one file at a time from you, go tools > options > uploads > slots. You can change the number of uploads per person there. Click apply to save the change.

2. You control what folders are being shared. Tools > options > sharing will show you which folders are being shared...you can change this at any time.

Are you getting any error messages when you try to play the movie? Have you tried using another player? This one's good & has codecs installed to play most file types: VLC media player

Did you check the movie with Bitzi before download? If it won't play at all, no matter what player you try, maybe it's just a crap file.
Bitzi Web Lookup

If you're getting error messages about missing codecs, use the forum search to look for codecs...you'll find heaps of info.