Most modern cameras have a sensor that knows the orientation of the camera and automatically rotates photos.
However, for older photo collections, you may have hundreds of photos that need to be rotated. Here is how to rotate groups of photos in Windows:
1. Go to your file manager. If you can't find it, hold down the Windows icon key and press the E key.
2. View the files in Large Icons or Extra Large Icons so you can see them.
3. Select the photos you want to rotate by holding down the CTRL key while clicking on the images you want.
4. Right-click and choose the direction in which you want to rotate.
The illustration below shows 3 of 4 pictures that have been selected (note the blue border) and the user is about to rotate them to the left.