FLV (Flash video) is a popular video format on the internet. Youtube videos and video content on many video sharing websites are in FLV format. If you have download such videos, then you either need special video player like VLC Player to play these videos or install addon to make Windows Media Player capable of playing such videos.
PlayFLV is a small and very effective addon for Windows Media Player. After you install this addon, all the FLV video will open and play in Windows Media Player by default. No need to select player, here on all your FLV videos will play in Windows Media player.