Index: /trunk/src/VBox/Runtime/r3/fs.cpp
===================================================================
--- /trunk/src/VBox/Runtime/r3/fs.cpp	(revision 78204)
+++ /trunk/src/VBox/Runtime/r3/fs.cpp	(revision 78205)
@@ -87,6 +87,13 @@
         fMode = (fMode & ~RTFS_TYPE_MASK) | RTFS_TYPE_SYMLINK;
 
-    /* writable? */
-    if (!(fMode & RTFS_DOS_READONLY))
+    /*
+     * Writable?
+     *
+     * Note! We ignore the read-only flag on directories as windows seems to
+     *       use it for purposes other than writability (@ticketref{18345}):
+     *       https://support.microsoft.com/en-gb/help/326549/you-cannot-view-or-change-the-read-only-or-the-system-attributes-of-fo
+     *
+     */
+    if ((fMode & (RTFS_DOS_DIRECTORY | RTFS_DOS_READONLY)) != RTFS_DOS_READONLY)
         fMode |= RTFS_UNIX_IWUSR | RTFS_UNIX_IWGRP | RTFS_UNIX_IWOTH;
     return fMode;