What you're dealing with is probably misconfigured permissions on that folder.
The solution could be as simple as disabling simple file sharing and correcting
the permissions issue. You might also need to take ownership of the folder in
order to set the proper permissions. Take a look at this article first.
Courtesy of Ramesh Srinivasan, MS-MVP
Access is denied when opening the Shared Documents folder
If that doesn't fix the problem, take a look at the information in these
"Access is Denied" Error Message When You Try to Open a Folder
How to take ownership of a file or folder in Windows XP