DIVX-avi files do not show in Windows explorer

Hi,
I have this strange problem :

I have a CD with a DIVX-avi file on it.
I can see the file when I explore the CD in WinXP and I can also play it
with WMP11 because I have installed the necessary codecs to do so (Mega Pack
from K-Lite).
No problem with WinXP thus.

My problem is with my Vista Premium machine :
When I explore the CD, I do not even see the DIVX-avi file. It looks like it
is not even there.

Any clue what the solution to this problem might be ?

Thanks
Geo