Most data recovery program search for deleted MFT entries to undelete files. These programs usually give a give a probability of recovery rating of 'good', 'medium' or 'poor'. What they are actually doing is locating the MFT record for a deleted file and then checking the rest of the MFT records to determine if the clusters that the deleted file occupied are being used by any other file stored on the computer. As only one file can occupy any one cluster on a hard drive, if other files are using your deleted files storage space then it is likely that the original data has been overwritten and permanently destroyed.
This recovery technique is usually relatively fast way to get data back, as all the recovery program has to do is find the deleted file entries in the MFT and then go directly to that location of the hard disk to perform the data recovery. You will see an MFT search when you execute a "Fast Search" using Recover My Files Data Recovery Software.
However, if your MFT is corrupt, defective or has itself been overwritten, this method isn't going to help you even though the file data still remains out on the disk waiting to be found. What you need to do is search unallocated clusters.
