My easiest answer to watching movies is to turn the TV on lol

You need codecs my boy (or girl): http://www.divx-digest.com/software/nimo_pack.html

Codecs are miniature programs that encode or decode media from one format to another.

As a back up player you might wanna get DivX player &/or VLC (which has inbuilt codecs, & free & plays all except the odd wmv file) http://www.videolan.org/vlc/ (choose the nearest mirror site.)

Happy watching