If you use a Secure Digital High Capacity card with a portable device such as a digital camera, it is generally best to format the card with that device to prevent the possibility of it being unrecognized when you insert it. If that isn't an option, however, you can format the SDHC card with your computer.
In Windows 7, you can select from the NTFS, exFAT and FAT32 file systems when formatting an SDHC card. FAT32 is compatible with most devices and non-Windows computers but does not allow storage of files larger than 4GB, while NTFS and exFAT remove the file size limitation but are poorly supported on non-Windows platforms. Microsoft designed the exFAT file system for removable storage devices such as SDHC cards; its reduced system overhead may produce better performance than NTFS on flash devices but operating systems older than Windows XP do not support exFAT.
Allocation Unit Size
The allocation unit is the smallest addressable space in which a device can store a file. For example, if an SDHC card has an allocation unit size of 64KB and you save a 32KB file on it, the file consumes 64KB on the SDHC card because one allocation unit cannot store multiple files. If you plan to store many small files on the SDHC card, a large allocation unit size can lead to wasted space. Conversely, a small allocation size can cause a slight performance reduction. Windows also provides a "Default allocation size" option that you can use if you aren't sure.
The "Volume Label" option lets you name the SDHC card, which then appears on the list of storage devices on the "Computer" screen in Windows. If you have several SDHC cards, you may find it easier to maintain organization by naming the card according to the type of content you intend to store on it.
The "Quick Format" option allows you to format your SDHC card nearly instantly. This option skips the standard checks that Windows performs for media integrity and simply deletes the file index from the device. A full format deletes all content from the device and checks for media integrity, but may take several minutes to complete.