cany watch movies

i keep getting file is not supported messages when i try to watch certain films i have 10 films and cant watch 5/10 how can i check what the problem is. i use windows player and real 1 player and ive got divx .... .

you can use a program called gspot to find the codec you need get it here http://www.headbands.com/gspot/download.html
you could also go with a kazaa lite codec pack kazaa is the best of the lot get that here home.hccnet.nl/h.edskes/finalbuilds.htm