Can't read pen drives or CDs... security problem?

In XP Professional, when I try to read CD/DVD drive or a pen drive, I
get the critical error "access denied", even if it reads correctly the
unit label or the type of CD (audio, for example). With right click on
those units, the sharing and protection option doesn't appear.
Trying it with the Administrator account it's exactly the same thing.
I exclude it's a HW or driver matter, because I have the same problem
with different types of device.