MPlayer

MPlayer is a program that allows you to play audio and video files of various formats, including AVI, ASF, WMV, MPEG, MOV, MP3 and WAV.
The player doesn't require installation and your Windows registry keys will remain intact, meaning it is portable. You can also place the tool on an external device and run it on any computer.
The application takes a few seconds to load, every time you initialize it. Its interface is familiar, so you shouldn't have any problems in using it.
You can insert files into MPlayer by using the file browser or the "drag and drop" method, as well as create and save playlists.
So, you can use basic media player commands, such as "Resume", "Stop", "Previous Track", "Next Track" and volume adjustment. You can also switch to full screen mode, set left and right volume level, and use an equalizer (brightness, contrast, hue, saturation).
The program uses a low amount of CPU and system memory. However, it doesn't include a help file, has a slow response time and every time you switch a video to full screen mode, you cannot exit it (the application freezes and you have to restart it).
All in all, MPlayer is a decent tool for playing audio and video files. It can even be used by beginners but it certainly needs some improvements.