Downloader tools can be quite unpleasent. It is often a choice between overcomplicated adware, or you have to use the vendors software that may not be very good. Downloading large files should be as simple and reliable as small files for the user. Perhaps Metalink[1] support would help?
There's plenty of uncomplicated, adfree software. For Windows, I'm partial to Miniget (which supports both HTTP and Bittorrent): http://www.miniget001.com/
There are 'downloaders' to deal with this kind of issue. That said, torrents are most optimal for a non-stable network connection.