allow add new hardware access to limited user account

how do I give user access so that normal users can access USB storage device
e.g USB key . Whenever user inserts USB device it pops up with add new
hardware window asking for Administrator username and password. I certainly
don't want to give them local admin access but I also want them to use USB
storage device . I couldn't find any Group policy to do this , nor adding
them to Powerusers group is of any help.


Thanks