Warning: Formatting a memory card will erase all the files on the card. Most devices that support flash memory cards (i.e., camera) are configured with a format utility.  Before using this format utility to format your flash card, it is important to first confirm the utility supports the flash card capacity and type. It's also important to ensure the file format structure (e.g., file allocation table) utilized by the device is compatible with any other device you might use the flash card with.  For example, if the camera formats in FAT32, you may not be able to use that flash card in a digital picture frame that only supports FAT.

If you are using a card reader and a PC to format the card, open "My Computer" in XP or "Computer" in Vista and Win7 and highlight the drive that corresponds to the card. Make sure you choose the correct drive letter. Next, right-click the drive and select "Format" from the menu with the left mouse button.

Choose the file system that is appropriate for the card capacity and the device you are using the card with. Flash cards 2GB and below should use FAT. Cards between 4GB and 32GB typically use FAT32.  However, if you plan to transfer single files larger than 3.99GB to the card or if you have a flash card that is 64GB or larger, select exFAT.

If you are using a card reader and a Mac, open the "Go" menu and double-click on Utilities (If you do not see Utilities, double-click on Applications and then double-click on the Utilities folder). Double-click on the Disk Utility icon. On the Disk Utility Dialog box, click once on the flash card's active partition.Note: There will be two listings for the card, the first one is the active partition and the second is the volume label. Click the erase tab located on the right side of the screen. Using the Volume Format drop-down, select “MS-DOS File System” from the list. Click Erase.