Secure digital (SD) cards are flash memory cards that hold up to 2 gigabytes (GB) of information; the new SDHC (SD high-capacity) cards hold up to 32 GB of information. You can transfer or copy files from one SD card to another through a PC or Mac. For a true clone, erase or format the SD card to which you plan to transfer the files.
Plug in the First SD Card
Due to SD cards' lack of power, you'll need to plug them into a device in order to access them. Place your SD card into an SD slot in a PC, or put the SD card into a USB adaptor and plug the adaptor into your PC's USB port. Your PC will interpret the SD card as an external drive. Depending on your desktop and card settings, the card will either open automatically to display contents or appear as an external drive icon on your desktop, or you have to find it in the folder tree through the "My Computer" icon on a PC.
Copy the SD Card Contents
Once you find the drive, open it to display all the folders or files within. The folders contained on the SD drive will appear in the open window. To copy all files, select all of them at once and then copy. In Windows, under "Edit," choose "Select All" then "Copy." If you only have one slot or USB connection, copy the files to a new folder on your hard drive. Create a new folder, then open the folder and "Paste" the copied files into the new folder. If you need the slot or USB connection for the second SD card, remove the first SD card.
Plug in the Second SD Card
Plug in the SD card onto which you want to copy the files. When you find the icon for the second drive, right-click on the icon without opening it, then choose "Paste." The files you copied from the first drive will now copy to the second drive. If you right-click on the second drive and the "Paste" option does not appear, recopy all the files and folders from the first drive, click on the icon for the second drive and click "Paste." Compare the folders from the first drive with the folder on the second drive to ensure that they are identical. Erase the contents of the second SD card before you copy the new files if you want the SD cards to have identical contents. If the second card already contains some of the files you have attempted to copy from the first drive, a window will open asking whether you want to replace the old files with the new files from the first SD card. Click "Yes."
On a Mac, insert the SD card/adaptor into the computer. When the white USB drive icon appears, double-click on it to open it, then copy the files. Paste the files onto the desktop or directly onto the second drive.
Cloning the SD Card Contents
To make the second card identical to the first card, plug in the second card, erase all the contents, then proceed with copying the first card's contents to the second card. To reformat the second card to exactly match the first card's formatting, right-click on the icon for the first card and then view "Properties" to see what file system it uses. Right-click on the second card's icon (before you copy files to it), select "Format" and choose the same file system as the first card's. Then proceed with copying the files to the second card.