windows media xp

This is my first time trying to download movies but my windows media will not let me play them it says i do not have the right codec does anyone known which ones i need or how to tell the link on this page does not work to tell you how you can tell which ones you need.

Windows Media player supported file types:
CD audio: *.cda
Windows Media audio and video files: *.asf, *.asx, *.wax, *.wm, *.wma, *.wmd, *.wmp, *.wmv, *.wmx, *.wpl, and *.wvx
Windows audio and video files: .avi and .wav
DVD video: *.vob

you can use imtoo mpeg encoder, it supports many file formats. see here: http://www.sharewareguide.net/Audio-Multimedia/Video-Tools/imtoo-mpeg-encoder.html

ive bin downloading movies for a little while but just recently after downloading one i tryed to play it and it wouldnt play in windows media player (which is where i watch all my other downloaded movies etc)i thought it was just the file and tryed opening it with a couple other programs and none of them worked apart from divx which played it fine the thing is most of my video files wont play now even ones which which i know were fine and played perfectly before it says the error is with divx does anyone know how to fix it?
the error signature that comes up when i try and play video files now is
AppName: wmplayer.exe
AppVer: 11.0.5721.51.5145
ModName:divxdec.ax
ModVer:6.5.0.0
Offset: 0030c32

Go to this site and download a decent codec collection like I have: All in One, Xvid, DivX, Xp, Satsuki Decoder, FFDSHOW, and for sound AC3 filter. Also some good players like VLC and Media Classic (included in Satsuki). http://www.free-codecs.com/ To make Bjarne happy some codecs are on this site too.