Howtogeek posted a tutorial about access files from SD cards in modern Windows 8 apps

Modern Windows 8 Apps such as the Xbox Music, Xbox Video, and Photos apps can only display content stored in your libraries. You may want to store media files on an SD card or USB drive, but Windows stops you.

To get around this limitation, you will need to make the SD card or USB drive accessible at a different location in Windows. This will trick both Windows 8 and Windows RT into allowing you to add it to libraries.

  How to Access Files From SD Cards and USB Drives in Modern Windows 8 Apps