Real "streaming" is not possible easily (without preparation on the server side). When actually
streaming, the client does not download the entire video, but only buffers part of it to replay it one the fly, and the server is sort-of broadcasting the data stream. After having played the content, the data is dumped automatically. What you're looking for is something else: you want playback to start immediately, after the download has started. This is often confused with "streaming", that's why you will find several google results that apply to your situation when you're actually looking for something else. If you want details on streaming itself (won't help you much in your situation though, but only makes interessting reading for those who are curious), start with the Wikipedia article
http://en.wikipedia.org/wiki/Streaming_mediaAs Phill suggested, MPEG files are actually not the best choice for immediate playback and buffering. Windows media video format (wmv) performs well in this aspect and gives nice compression results, and it has got a great andvantage: the encoders are available for free. Nearly everybody can play wmv, as nearly everybody has got MS Windows. The drawback is: it's a proprietary format. That's why I said "nearly everybody". The same thing applies for real media and apple quicktime: they have great codecs, they perform very well, but not everybody has got the needed software applications to replay them out of the box. There are several good reasons why users can't/won't separate plugins or applications that enable them to view particular media (e.g. corporate policies, concerns about security and system performance, technological issues etc.). That's why Youtube and all the other video sites use Flash videos: most users on the internet have a flash plugin installed in their browsers. Flash video works comparatively well as far as buffering is concerned. The only drawback is the effort needed on your side to encode flash videos, i.e. you need to convert your videos to flash video and you need to add a plugin to coppermine to play flash videos.
Joachim