Normally, when a folder is shared the sub-folders inherit the permissions of that folder. That is, if someone can access the folder they should also be able to access any sub-folders.
The following describes how set the permissions of a sub-folder to be different to those of a parent folder.

1. Click on Start, Programs, Accessories and Windows Explorer
2. Right click on folder that is to be setup with different permissions and click Properties
3. Click Security and unclick box marked 'Allow inheritable properties..'
4. A warning message appears, to allow only the owner (make sure you know under which id the folder was created) to set the permissions click Remove. Otherwise click Copy.
5. Logon as owner or, if Copy was clicked in the last step, a user already defined with full access
6. Using Windows Explorer, right click on folder and click Properties
7. Click security and Add users