could be the file is corrupt,but more likely you are missing certain codecs.
Download VLC Player and Media Player Classic,these are the only media players I use,they will play nearly all the various formats available .
WPA2 hack: How secure is your Wi-Fi?
Add Depth Of Field to a photo using Tilt Shift Blur in Photoshop
iPhone tips & tricks
Comment afficher des fichiers cachés sur Mac ?