nFLVPlayer plays FlashVideo(tm) format also known as flv. This player offers common video player functionality controls. As an addition there is an OSD display, Smoothing function, and most recently accessed files/URL's list. Since version 1.1+ nFLVPlayer offers fullscreen playback and picture adjustment filters: brightness, contrast, saturation and hue.
You need a flash plugin installed on your system in order for this player to work. The oldest flash version that nFLVPlayer supports is Flash 7 which imposes some limitations and may not play all possible videos because it lacks codecs for the newest. I recommend installing flash 9 as it has quite alot of improvements in performance.
Note that FlashVideo is generally very CPU consumming so heavy bitrate video might need faster CPU accordingly.