Recovery Pro first requires the creation of a carbon disk image copy of your memory card. So if you have a 64GB card, then you need 64GB space on your system (Internal or external) to make that image. We then recover files from that disk image. So, if your card was full, then you will need another 64GB space for recovery for a total of 128GB available on your disk. In general, it is a good practice to have twice amount of space on your hard drive, in comparison with your memory card density.