The convertor I have is riverpast video cleaner.
You're likely working with a compressed AVI file. My advice is to convert it to an uncompressed AVI file. If you downloaded this from anywhere and it's an AVI file I garauntee it's compressed in some way.
Also try installing these codecs and seeing if the files play in premier afterwards http://www.free-codecs.com/download/...codec_pack.htm
get the full version. Install, follow instructions, see if after you install this you can use your vid, a lot of the times we don't have the proper codecs installed for our programs to decipher the information in the video so that you can edit it.
It could also be that the file is unusable, it happens from faulty/inconsistent compression, when I made my Silva vid I couldn't use the Maia fight or the Irvin fight cuz they were unreable by all my programs, it sucked :/
As for where people get their vids I dunno, I suppose torrents are a good place, but they have a multimedia section here as well with RS links and whatnot, I used that for my vid. They have a lot of links on this site, look around the multimedia videos section and use the search feature to find what you want.