To format a USB drive you must be logged on using an account with administrator privileges. Please see the instructions below to reformat for your PC, or Mac system.Windows (XP, Vista, 7, 8)While logged on using an administrator account, connect the USB drive to your USB port.Open the 'My Computer' (XP), or 'Computer' (Vista/7) window.Right-click the drive letter for the Centon USB drive, then click 'Format'. The default options should fine.drives up to 2GB - default filesystem = FAT;  drives 4GB to 32GB - default filesystem = FAT32;  drives 64GB or larger - default filesystem = exFAT;  Note: exFAT filesystem requires Windows 7, Windows Vista SP1 or newer, or Windows XP SP2 or SP3 with Hotfix KB955704.  The default filesystem can be modified if desired - just select the filesystem of your choice from the drop-down menu.  [FAT32 limits file size to less than 4GB; if you have files 4GB or larger, use exFAT or NTFS.Optional: Untick the option for 'Quick Format' to perform a full format (format may take considerably longer time to complete).To begin the format, click the 'Start' button, then click 'OK' to confirm that you really want to erase all data; the drive will be formatted.Once the format completes, you should be able to write or delete files on the flash drive without incident.MacConnect the USB drive to a USB port on your Mac.Launch Disk Utility, located in Applications > UtilitiesLocate the Centon USB drive from the left hand side of Disk Utility and click on it.Click on the 'Erase' tab across the top.Choose the desired format. (see below)FAT - on Mac, FAT can be used on nearly any capacity USB drive.  [FAT may limit file size to less than 4GB; if you have files 4GB or larger, use exFAT or Mac OS Extended (Journaled)]."Mac OS Extended (Journaled)", a.k.a. "HFS+" - If you plan to use the drive on Mac computers only, this is the recommended file system. Drives formatted with this file system cannot be read on Windows or other PC's.ExFAT - format to this file system if your computers meet the requirements:Mac - requires OS X 10.6.5 or laterWindows - requires Windows 7, Windows Vista SP1 or later, and Windows XP SP2 or SP3 with Hotfix KB955704Name the drive if you want, the name can be changed at any point.Click the 'Erase' button and confirm again on the next pop-up window.Once the format completes, you should be able to write or delete files on the flash drive without incident.For SD Cards,Centon Tech Support recommends using the SD Card Organization's software tool for formatting SD, SDHC and SDXC media.SD Formatter 3.xx for SD/SDHC/SDXChttps://www.sdcard.org/downloads/formatter_4/