Unexpected ambiguity in image aspect-ratio

Question

I have recieved by email, than downloaded, the picture that you can see opened with Photoshop in the screenshot below.

That picture was created - and was meant to remain - wider than high.

How come Photoshop "sees" its height bigger than its width?

I add the detail that, opening it only with some software (Paint, Picasa viewer,...), I see the picture squeezed horizontally of about 50%: this way, width is smaller than height to my eye too.

Any help/hint to understand the reasons and to avoid such ambiguity in viewing?

Answer 1

I have now found out what was making the problem occur.

Right-clicking the image icon one can access the image/file properties, on Windows OS.
Properties > Details > Image: here I found horizontal and vertical resolution.
Since the first was set to 200dpi and the second to 400dpi (by mistake in this case!), the image aspect-ratio appeared to be altered from what was expected. It was now very easy to edit such couple of values using - for example - Photoshop's Image size menu.