lordnick5000: It would help to know which OS you use. Yo uprobably need moe codecs for your video player: http://www.divx-digest.com/software/nimo_pack.html
OR get a free video player that plays all types of video (has inbuilt codecs) except the odd wmv file that has licencing: VLC (a free player - click on link) & make this your default player do everytime you browse a video vlc will play it. Good luck lord