Access Denied

My client have 3 notebooks connected together in network using peer to peer under Windows XP Pro, SP1. All notebooks local drives are shareable. All users have administrator right. Two notebooks can access all files and folders except Program Files Folder on the 3rd notebook. Both notebooks get exact same error message “ACCESS DENIED” when trying to access Program Files folder on 3rd noteboook.

What I need to do to get through Program Files Folder?