Should one recover or repair a failed disk?
There are many programs that will attempt to repair a failed disk, or maybe just undelete files that have been deleted. The quick answer to this question, is do not touch them if your data is valuable.
How disks get repaired
A disk can be repaired by finding the problem and correcting it. For a deleted file, this may be isolating where the file was stored, read the data and then save the file. The problem with this is that the first deleted file will be recovered OK, but when it is saved, the location it is saved in is in effect random. ie The operating system decides where to save the file and has no knowledge of where the old file was saved, or where the next file to be recovered is saved. This it is quite possible for the recovery of one file to overwrite data that has not yet been recovered.
Why CnW does not allow processing of C: drive
To help try and prevent the above issue, CnW does not allow access to the C: drive, or Physical Drive 0: These are typically the system drives and often written to. The operating system writes lot, sometimes as temporary data, or system updates. CnW stores logs that by default are on the C: drive. Thus the way to recover from the C: drive using CnW software is to remove the drive and set it up a slave on a different PC.
CnW does not consider drive repair as an option - the only exception would be the single boot sector (MBR), but then only with care. The following stages are the recommended method
1) Create a disk image. This could be considered optional but should always be done if the disk is failing, or recovery is part of a forensic application. An extra safety stage would be to read the disk with a write blocker.
2) Recover the files onto another disk drive
3) Only when 110% sure of full recovery, possibly copy files back to original drive.
4) Retain copy of the original image for a suitable period of time, in case stage 3 was not correct.