Windows Media Player- Is a technology that produces streaming video and audio files. The WM player will play most types of movies including its native Advanced Streaming Format (ASF), WAV, AVI, Quicktime and RealOne formats. A good all-around choice.
Quicktime- An audio/video technology developed by Apple, but can also play on any PC. Its versatility and quality of playback are outstanding and its ability to compress large movies into small files is remarkable. You don’t need the professional version to watch video, just download the free one.
RealOne Video- A streaming technology developed by RealNetworks for transmitting live video over the Internet. RealVideo uses a variety of data compression techniques and works with both normal IP connections as well as IP Multicast connections. You don’t need the professional version to watch video, just download the free one.