Shutdown prompt me for a password ?!!?

[lorenzo zampese notes electrolux it]

When I run 'shutdown -h now' or 'halt' as a normal user (not root),
it prompt me for a password that I don't know (it isn't the root's password).
I changed the 'x' attrib of 'shutdown' with 's', but it still prompt me
for that password.

I would like to avoid this password.
Can anybody help me ?


Thank you.