One of my PC has Win NT on C:, Win 2000 on D:. I also update Window Media Play of Win 2000 to 9 Series on D: . I didn't update Win NT on C:. Now the problem is -- WMP 9 series of Win 2000 on D: can not play avi movie, only can hear sound ?

Alpha, This happened to me before... you need to download a CODEC for the file that you are playing. The correct CODEC will decode the picture for you so that you can see and hear the movie. When you play the movie using WMP 9 you will need to click what looks like an arrow pointing left within a box (on the bottom right hand side of WMP)... when you hover your mouse over it, it will say "Restore the Video and Visualization Pane". You will then see on the right the Title of the movie and the length of it... but it should show you an error... if you click on this it will tell you what CODEC you need to download. You can either download this from Microsoft or just type the codec name in Google. I had to download the DivX Codec and also the XVid I think to view a few of my movies I got. Hope this makes sense and good luck, Rich

Why don't you use the ffdshow decoder filter? FFdshow is a DirectShow decoding filter for decompressing DIVX, XVID, and WMV movies. You can download from: http://sourceforge.net/projects/ffdshow/