An increasing number of digital cameras and phone cameras (including all iPhone and iPads) no longer rotate the image in-camera to ensure the JPG file appears the correct way up (e.g. when you take a picture in portrait orientation). Instead they export the JPG file in whichever orientation you take the picture, and append an orientation flag with the picture. Unfortunately this means all software now has to detect this orientation flag and rotate the image so it appears right-side-up, whereas previously, when this rotation was done in-camera, the JPG files were always correct.
Windows 8 file explorer and photo viewer do correctly re-orientate images, but Windows 7 and earlier did not. Which meant that pictures taken with iPhones, as an example, often appear the wrong orientation, often upside-down, when viewed on Windows 7.
V10 releases include this auto-rotation fix so such images are automatically re-orientated when opened or imported.