Most Micro SD Cards and standard SD Cards 32gb or larger (SD, SDHC, SDXC) can only be formatted as exFAT or NTFS on Windows. This is actually a good thing in general as it means you are not stuck with the 4gb file size limit of FAT32, also Windows, OSX and Linux can all read and write to exFAT. So why would you want to format a large SD card to FAT32? The simple answer is you probably have a device that can not read exFAT, such as the Nintendo 3DS. The easiest way I have found to format an SD card to FAT32 on modern versions of Windows is to use a command line application called FAT32 Formatter. This command line application does as the title says, allows you to format drives to FAT32 using Windows. How to format an SD Card to FAT32: 1. First Download FAT32 Formatter 2. Unzip FAT32 Formatter somewhere, in this example i unzipped FAT32 formatter to C:\fat32format 3. Open a Command Prompt window with Administrator rights, this can be done by right clicking on Command Prompt in the start menu or start screen and selecting "Run as Administrator" 4. You need to be working in the FAT32 Formatter directory, so type cd C:\fat32format (presuming you unzipped FAT32 formatter to the same place as i did) 5. Look in My Computer and make a note of the drive letter that has been assigned to your SD Card, for me this was G: 6. Then simply type fat32format g: (replace g: with the drive letter your SD Card was assigned) and type yes to confirm the format: 7. After a few seconds your SD Card should now be formatted as FAT32 and usable in devices such as an Nintendo 3DS: That's all, you have formatted your SD Card to FAT32!