Holy cow, I wrote a book!
It's actually a signal to Explorer to look harder.
It doesn't mean that the directory is read-only.
If a folder has the Readonly or System flag set, then Explorer will look for a desktop.ini file
which describes the folder customizations. For performance reasons, Explorer does
this only if the directory has the +R or +S flag. (This is enormously important on
There are two KB articles on this subject, and I will defer to them for much of the
discussion. This is the version
that applies to Windows XP and Windows Server 2003. There is also a
version that applies to older versions of Windows, although the UseSystemForSystemFolders policy
Coders shold use the function PathMakeSystemFolder to mark a folder as
requiring special attention from Explorer.