[AUCTeX] Unable to preview images

[José Carlos Santos]

Hi all,

I am unable to preview images with Emacs 24.5.1 + AucTeX 11.89, working 
under Windows. Whenever I try to do that I get the "preview-image-type 
setting 'png unsupported by this Emacs" error. Why is that? It is 
written at ftp://ftp.gnu.org/gnu/emacs/windows/README that

      PNG: requires the PNG reference library 1.4 or later, which will
      be named libpngNN.dll or libpngNN-NN.dll.  LibPNG requires zlib,
      which should come from the same source as you got libpng.
      Starting with Emacs 23.3, the precompiled Emacs binaries are
      built with libpng 1.4.x and later, and are incompatible with
      earlier versions of libpng DLLs.  So if you have libpng 1.2.x,
      the PNG support will not work, and you will have to download
      newer versions.

Therefore, I should already have PNG support. What am I missing?

Best regards,

José Carlos Santos