FAT is a computer file system architecture now widely used on most computer systems and most memory cards,NTFS is the standard file system of Windows NT.

FAT and NTFS possibly artificial or natural damaged,in this case,do you think we just need reformat hard drive?If you want to format hard drive,make sure you will not lose data.Otherwise,you need recover files after format hard drive with some data recovery software
and then reformat hard drive as NTFS or FAT32 file system.

FAT-File Allocation Table is a computer file system architecture now widely used on most computer systems and most memory cards, such as those used with digital cameras,usb flash card.The FAT file system is relatively straightforward technically and is supported by virtually all existing operating systems for personal computers.What the people are commonly used is fat16 and fat32.
FAT16-Compaq DOS 3.31 (an OEM version of MS-DOS 3.3 released by Compaq with their machines) introduced what is today called the FAT16 format, with the expansion of the 16-bit disk sector count to 32 bits.In order to overcome the volume size limit of FAT16, while still allowing DOS real mode code to handle the format without unnecessarily reducing the available conventional memory.
FAT32-Microsoft implemented a newer generation of FAT, known as FAT32, with cluster values held in a 32-bit field, of which 28 bits are used to hold the cluster number, for a maximum of approximately 268 million (228) clusters.In order to overcome the volume size limit of FAT16, while still allowing DOS real mode code to handle the format without unnecessarily reducing the available conventional memory.

NTFS is the standard file system of Windows NT, including its later versions Windows 2000, Windows XP, Windows Server 2003, Windows Server 2008, Windows Vista, and Windows 7.NTFS supersedes the FAT file system as the preferred file system for Microsoft’s Windows operating systems. NTFS has several improvements over FAT and HPFS (High Performance File System) such as improved support for metadata and the use of advanced data structures to improve performance, reliability, and disk space utilization, plus additional extensions such as security access control lists (ACL) and file system journaling.NTFS compresses files using a variant of the LZ77 algorithm.The Volume Shadow Copy Service (VSS) keeps historical versions of files and folders on NTFS volumes by copying old, newly-overwritten data to shadow copy (copy-on-write).While the different NTFS versions are for the most part fully forward- and backward-compatible, there are technical considerations for mounting newer NTFS volumes in older versions of Microsoft Windows. This affects dual-booting, and external portable hard drives.
The Volume Shadow Copy Service (VSS) keeps historical versions of files and folders on NTFS volumes by copying old, newly-overwritten data to shadow copy

FAT is easier damaged than NTFS.So maybe there are more times to restore FAT drive.

If people want to reformat hard drive as NTFS file system or FAT32 file system,the only thing you must be careful is that you should backup your important files like photos,videos,documents.If not,you will lose them and need recover them with data recovery software.