> Date: Fri, 10 Apr 2015 05:32:49 -0500
> From: Mario Valencia <mariovalspi@gmail.com>
>
> On the previous emacs 24.3 it png files display just fine with libpng14-14.dll.
> On emacs 24.4.1 on windows 8, all png files give an error: "Cannot display
> image: (Invalid image specification)". Other images, like jpg display fine. I
> have this files in the emacs bin directory: (as you can see i have
> libpng-16-16.dll)

What does this produce:

  M-: (image-type-available-p 'png) RET

And what does this produce:

  M-: libpng-version RET

And finally, how about this one:

  M-: dynamic-library-alist

> -rw-rw-rw- 1 mario mario 72192 03-11 11:36 zlib1.dll

This DLL's size is much smaller than what I have on my machine;
perhaps this is your problem?  (libpng depends on zlib1.dll.)  Make
sure you use the one that came with libpng.