Cannot access folder "Access Denied"

In cases when you need to access folder, but get "Access Denied" message even when you're logged on as an Administrator, you'll have to take ownership of that folder.
To do this in Windows Server 2003 open folder Properties, select Security tab and click on Advanced button, then hop on Owner tab. Now select user which will be the new owner of this folder and click OK (screenshot).

Links:
http://www.lockergnome.com/windows/2005/10/04/take-ownership-of-a-folder-in-server-2003/

When viewing shared folder contents users should be able to see only those subfolders they have access to

When you have shares for multiple users, each of whom have permissions to different subfolders in that share, you might want to filter the view that the users would only see those contents which they can access.

To achieve this on Windows Server 2003 you'll need to install Access-based Enumeration.

When installed right click on the shared folder, go to the Access-based Enumeration tab and check the Enable access-based enumeration on this shared folder checkbox (screenshot).
Click Ok.

Downloads:
Windows Server 2003 Access-based Enumeration
Documentation

Shares and subfolders permissions

Task:
Share a folder and make some of its subfolders available to one user group and not available to another user group which also has share permissions on the root folder.

The difficulty in this was that if I share "Folder 1" for "user group 1" with full permissions, then this "user group 1" is able to access all of "Folder 1" subfolders. It is because "Folder 1" inherits the "Security" permissions from it's root (in my case it was "Users (DOMAIN\Users)" with Read & Execute, List Folder Contents and Read permissions on "D:").
You need to remove these inheritable permissions.

To do this:
Right click the shared folder "Folder 1" and click on Properties.
Go to Security tab and click on Advanced button.
Clear the Allow inheritable permissions from the parent to propagate to this object... checkbox (screenshot).
At the prompt click Remove to remove inherited permissions (screenshot) and then specify your own.