Hello there, welcome to Seven Forums.
I'd recommend
VLC media player, it's one of the best media players out there. Willl play almost any video file without problems & it doesn't need any codec installation.
You can also try out any of the following:
mplayer - it's an alternative to VLC, but not quite as popular.
KMplayer - this one doesn't require codecs to be installed either.
Windows Media Player , Winamp, Quicktime/iTunes, DivX Player - some of these might need codecs
to play video files.
Codec Packs K-Lite Codec Pack - the best comprehensive codec pack available.
Combined Community Codec Pack - an alternative to K-Lite.