images when they are visited or inserted into buffers if Emacs can
display the relevant image type. File names matching
@code{image-file-name-extensions} or @code{image-file-name-regexps} are
-considered to contain images.
+considered to contain images. Note that Emacs can only display images
+of the types for which the appropriate support libraries were linked
+into Emacs when it was built. In particular, the MS-Windows version
+of Emacs doesn't support image files as of version 21.1.