Skyrim: how to kill a dragon

I was riding on horseback during a starry night, when when I was attacked by a dragon. Last video of Skyrim The Elder Scrolls V 1680x1050 with nvidia 8800gt Screen resolution: 1680x1050 PC configuration e6750@3.2 ghz cpu nvidia 8800GT 512 mb Asus P5K 4gb ram The nvidia driver was GeForce 285.62