Filesystem Ownership

[Laurent Asorne]

Hi! I'd like to change the ownership of my Sony Microvault 1GB USB Memory 
Stick, but everytime I try with
# sudo chown laurent:users /media/MICROVAULT/

I get the following error message:

chown: changing ownership of `/media/MICROVAULT/': Operation not permitted

I don't know what that means because actually ls -l says that user=laurent but 
group =root, so I thought that I could still change myself the ownership...

Can anyone help, please?
Laurent Asorne
-- 
You have a strong desire for a home and your family interests come first.