If its an NTFS directory, you can right click on the folder from mycomputer and then access the security tag.

Its quite likley that the whole disk has the 'everyone' security set, and each subfolder is getting permissions from its parent.

you should look at the root drive (d: or c and remove the everyone field (perhaps setting it to a minimum of authenticated users) remove.

On the user directory, remove inheritable permissions and set for only the user (and perhaps admin) to have rights