Corrupted file system ... how to retrieve data from file.CHK? 5 software to repair the damage!

Sometimes, unfortunately, it may happen that the operating system (Windows) is no longer able to read some files. This typically happens because the file system has been damaged because of a problem software and / or hardware.
Unfortunately, it is not always possible remedy easily and, depending on the files or folders that have been damaged, it may become impossible booting the operating system!
Example: Checking the File System on Disk C:
The various versions of Windows (98, XP, VISTA, SEVEN, 8) over time have increased their level of security, and in the meantime the file system has changed (from FAT, FAT32, exFAT to NTFS) and has increased the its robustness to errors.

"Under FAT or HPFS (1), if a sector that is the location of one of the file system's special objects fails, then a single sector failure will occur. NTFS avoids this in two ways: first, by not using special objects on the disk and tracking and protecting all objects that are on the disk. Secondly, under NTFS, multiple copies (the number depends on the volume size) of the Master File Table are kept." Microsoft Source
Note (1): HPFS file system is introduced with OS / 2. HPFS is only supported in Windows NT versions 3.1, 3.5 and 3.51. In Windows NT 4.0 is not supported, nor is it allowed to access HPFS partitions.

Even today, some computers have storage devices that use File System older and less secure (FAT). More simply, many of us often use USB keys that are usually pre-formatted with FAT32 (not NTFS).

When problems occur in the file system, often already during system startup or when you insert a USB flash drive, the operating system performs automatic procedures that attempt to correct errors using the controls and procedures are already in Windows:

1) Chkdsk: from a DOS command that checks and tries to repair the file system. For example chkdsk c: / ​​F / R

2) Scandisk: a Windows program that checks and tries to repair the file system. For example Scandskw.exe

If these steps fail to "fix" the file system often creates a hidden folder FOUND.000 that contains all the files or file fragments recovered. They are renamed in the form FILExxxx.CHK, where xxxx is a sequential number.

Files with the extension. CHK (Checkpoint) identify precisely lost file fragments and often contain files mixed together so unusable.
Unfortunately, this type of extension does not facilitate the inspection of the files to see if they are still usable or not, but they can rush to the aid specific software (some free) that help in retrieving data such as:

2) FileCHK Martin Kratz (download from the website of Eric Phelps)

3) CHK-Mate of DIY DataRecovery 

All these software examine and replace the extension of file.CHK with the most appropriate depending on the nature of the files (photos, documents, music, etc..). In this way it is easier to open and check if they are valid.
In some fortunate cases the file is in fact intact and usable!

There are also other Shareware software (for a fee), but for which I have NOT been able to verify the effective capacity...

5) CHK File Recovery of CHEAP Recovery Solutions

Finally, for those who want to examine the contents of your files manually (e.g. with Notepad) I recommend watching the first few characters of the file and compare them with the legend below to understand the nature of the files examined and associate the correct extension.

PK: compressed file (.ZIP)
MZ: executable (.EXE,.DLLs, .OCX)
BM: image (.BMP)
GIF89: image (.GIF)
II: image (.TIF)
Rar!: Compressed file (.RAR)
By: Microsoft Office files (.DOC, .XLS)
ITSF: compiled HTML file (.CHM)
% PDF: Adobe Acrobat file (.PDF)
‰ PNG: image (.PNG)

Supports most fragile and sensitive to problems of file system are USB flash drives and external USB hard drives, especially when using the old FAT system. Often the errors on the file system appear after you have removed the USB stick from your PC without first having "disconnected" with the specific function of Windows system tray, especially when the operating system was still copying or saving data on the stick or still had open files on it.

I remember one day in a USB flash drive (FAT32) used with Windows XP, I happened to lose the contents of an entire sub-folder (which showed "strange" characters instead of the name of the file). By inserting the same key on a PC with Windows 7, the OS I was properly warned of the problem and unfortunately "correct" File System automatically transforming however corrupt files on more than 1300 files with. CHK!
Thanks to the above mentioned software are quickly able to recover at least a portion of the documents from 1300!
Then I used a utility for Low Level Formatting (Low Level Format) to clear the entire contents of the key, and reuse the usb stick, see here: HDD LLF: how to low level format the hard drive.

Council No. 1: when you buy a new USB stick, which occurs with the operating system will use mainly:
  • If you use them only as a support for exchange between multiple PCs with different operating systems (XP, VISTA, SEVEN) then you need maximum compatibility then leave it as it is (pre-formatted FAT32).
  • If instead you use to store important data (such as backups) and mostly with 1 PC and 1 single operating system (eg Windows 7) then re-format it immediately into NTFS (New Technology File System), as the latter is more robust to errors. It 's true that NTFS loses compatibility with some older PCs, but there is for them a special reading software (NTFS Reader for Win 95, 98, Me).

Council No. 2: If you have hard drives or USB PC that already contain some data (FAT32 file system), you can convert it to NTFS without losing data by using the system command convert. For example, to convert the C: drive just writes from the command prompt: convert c: / f's: ntfs