click Start from your desktop bar and then select Run. In the window that opens, type cmd and press Enter. Enter command below (here the sd card is assumed to be G) and press Enter.
attrib -h -r -s /s /d g:\*.*
You can copy the above command by right-clicking the command prompt, selecting copy, and pasting it. However, you must replace the letter G with your sd card drive's letter. Return to the sd card drive check if the files appear.