hard disk data recovery

Very Useful Tool: winhex
  WinHex is in its core a universal hexadecimal editor, particularly helpful in the realm of computer forensics, data recovery, low-level data processing, and IT security. An advanced tool for everyday and emergency use: inspect and edit all kinds of files, recover deleted files or lost data from hard drives with corrupt file systems or from digital camera cards.
  Data recovery
for erroneously deleted files or generally after an experienced loss of data. Can be done manually (see undeleting files) or automatically. There is an automatic recovery mode for FAT12, FAT16, FAT32, and NTFS drives called "File Recovery by Name" that simply requires you to specify one or more file masks (like *.gif, John*.doc, etc.). WinHex will do the rest. Via the Access button menu, a recovery mechanism is available for FAT drives which re-creates entire nested directory structures (details here). Another mechanism ("File Recovery by Type", formerly "file retrieval") can be used on any file system and recovers all files of a certain type at a time. Supported file types: jpg, png, gif, tif, bmp, dwg, psd, rtf, xml, html, eml, dbx, xls/doc, mdb, wpd, eps/ps, pdf, qdf, pwl, zip, rar, wav, avi, ram, rm, mpg, mpg, mov, asf, mid. In particular owners of digital cameras quite often encounter problems with their media. WinHex is likely to help with this automated function that
 makes good use of the existence of file headers (characteristic signatures at the beginning of a file). Tools | Disk Tools | File Retrieval
  http://www.x-ways.net/winhex/allfeatures.html