Hi Claudio,
I am having the same problem after recently upgrading to Win10. Luckily I don't have that many photos so I will be manually modifying the photos so they have the correct orientation. From what I can deduce, the problem stems from Windows respecting
the properties in the file itself. In some of my photos it shows the dimensions 2592x1936 (WxH) for photos in landscape, while the reverse for portrait (1936x2592). Using option 1 below reverses these numbers.
So rightly or wrongly that's what it appears to be doing.
I have two options you could try:
(1) Using the Rotate Left and Rotate Right in Windows Explorer:
There are two rotation options: Rotate Left and Rotate Right on the Manage tab in Windows Explorer. You can use either function on multiple photos at once by holding down the Ctrl key and selecting all photos that need to be rotated in the same direction
(e.g. all need to rotate left) with the left mouse button. After selecting all the photos, click the Rotate left (or right) button to modify all photos at once.
Now from your response, you didn't seem too keen on the idea of modifying photos manually. So... on to option 2.
(2) Use Third-Party Apps Like JPEG ExiF AutoRotate: Depending on what metadata is stored in your photos, you might want to try JPEG-EXIF Autorotate to do the entire folder automatically. It uses the Exposure Program property in each
file to determine the rotation.
Right-click on a photo and select Properties. Then select the
Details tab. Scroll down to the Advanced Photo section and look for
Exposure Program. Hopefully it says Portrait or Landscape on yours. For mine they all showed Normal. So I am out of luck here.
Here is a link to how it works:
http://www.guidingtech.com/12182/auto-rotate-digital-camera-photos/
And here's the link to the site itself:
http://savolai.net/software/JPEG-EXIF_autorotate
Hope that helps.
Drax