Was following your tutorial on setting up a bunch of folders on Windows 7 machine to be shared with XP machines, and it was all going well. The permissions tab showed an entry for Everyone, and I had set that to Full Control, and Windows 7 started to change the permissions on the items and subfolders ... when suddenly, it stopped and said I don't have permissions to change the contents of a subfolder!
What gives? I didn't see where you had to launch the security tab with elevated privileges in order to set permissions.
Update: somehow, some of the folder got set to limited permissions. When I reset all the folders to allow full access for everyone, I could access them again.
Also, warning for those few who care to read this ... the machine is a dual-boot, having both XP and Windows 7 installed on it. Permissions set when running Windows 7 directly impact what you can do later when booting into XP!! Yeah, I know that should NOT be possible, but I tested it several times and was able to confirm when I limited permissions on a folder in Windows 7, and then booted into XP, I was not longer able to change files in that folder in XP.