The easiest method is scanning the SD card with Easeus Data Recovery. It will let you recover 1GB for free. After that you need to pay for a serial key.
The freeware way would be to do the steps here. Do not write anything as noted in the guide. Download Testdisk for Windows 6.14 and unzip to a folder on your desktop. Do a Quick Scan and see if it detects any partitions on the drive. Press upper case "P" after highlighting any partition detected. If you see the files listed you can select them with the ":" key and then use the upper case "C" key to copy. Or you can use the "a" key to select all files. In Testdisk your SD card would probably iisted as sdb.
The default location of file recovery would be the folder you unzipped Testdisk to.
Edited by JohnC_21, 16 February 2015 - 10:04 PM.