Posted 21 September 2012 - 08:12 PM
I have not used sdelete so I don't know exactly what it can do. It is probably similar in function to Hard Disk Scrubber. Hard Disk Scrubber can do various degrees of overwrite from 1-stage simple overwrite to 9-stage DoD. It looks like FileShredder is very similar to Hard Disk Scrubber in that it does various degrees of overwrite and can wipe unused disk space.
To put my previous comments in perspective, on the web page of FileShredder, the guy seems sincere and adds the caveat "Please note that I can not give any kind of support for File Shredder. I did my best to make this software useful and as reliable as possible but I can't an." I think that sentence was probably intended to finish something like, "...I can't anticipate all circumstances and eventualities". At least he was honest. The same comment is probably true for any software written by minor companies or individuals, User beware. These are powerful utilities that make changes that cannot be undone, hence my previous warnings. Until you are sure it works for you, back up important files (not the ones being erased).
MFT is the Master File Table, a list of files and where all the parts of the file are on the HDD. When you delete a file, the actual file data is still on the HDD but the space is marked as unused in the MFT. However, the filename is still in the MFT. Over time, much of the original file data will be overwritten. I don't think formatting a HDD stops previous data from being recovered because it is only going to overwrite once. To all but the most determined that data is not recoverable after a format but it can be with forensic software and hardware as used by government agencies. To make data impossible to retrieve you have to use multistage overwriting which ensures the magnetic signature on each magnetic region (bit) cannot be traced back. When I throw away a HDD, I take the cover off and go at it with a 6lb hammer. Even the FBI can't put Humpty Dumpty together again.
1. To remove data from the unused part of the HDD (where some/all the old deleted files reside) you would do a free space scrub/wipe (eg with Hard Disk Scrubber). Any part of the HDD that is not allocated to an active file on the MFT is overwritten. This is also available as an option in CCleaner.
2. To remove old filenames from the MFT you would use something like WipeMFT. It simply removes the filenames from the MFT that are not currently active. It does not remove the file data, see step 1.
Once you have done the above, you would use Hard Disk Scrubber to permanently erase critical files. You don't really need to run WipeMFT again because Hard Disk Scrubber gives the files new names, Scrub_001 etc, before overwriting so the original names are gone for good. If you forgot to do a secure delete for some critical files, you would repeat steps 1 & 2.