For better utilization of disk space, the storage space on a hard disk can be divided into separated areas, is called as partitioning. If you have accidentally altered your partition to NTFS from FAT, then you will not be able to access old data from the FAT partition. Though you are not able to access the data, you can still recover it with the help of data recovery software. Data loss from partitions due to formatting, or deletion of the partition is more accidental in nature. Whereas a partition corruption can be caused by software malfunction or improper shut down of the system. This kind of data loss is largely referred to as loss of data due to logical cause.
If you have misplaced data after changing your file system to NTFS from FAT, you need to use partition recovery software that can restore data from FAT partitions. Some of the data recovery software available can retrieve data from both FAT as well as NTFS partitions. Data lost from partitions due to logical cause can be retrieved if the data is not overwritten by other files or programs. Overwriting take place when you create, write or store new information on the drive from where you have misplaced the data. In order to ensure that the lost data is safe you should stop using the drive any more till you recovers the data.
Once you have chosen which partition recovery software to use, take away the hard disk from the system and attach this to the hard drive of another healthy system. Download the data recovery software to the healthy drive. Most of the data retrieval software is easy to use and you can recover data by following the instructions given in the user manual.