Hard disk information editor DBR FAT32 File System Track Head cylinders CHS partition BIOS Hidden Sectors physical disk volume boot sequence offset root directory data areas table LBA address secondary corrupted unusable formatted MS-DOS Windows NT virus

 
Data Recovery PRO DATA DOCTOR

Home | Order Online | Downloads | Contact Us | Software Knowledgebase

it | es | pt | fr | de | jp | kr | cn | ru | nl | gr


Sample Chapters from book DATA RECOVERY WITH AND WITHOUT PROGRAMMING by Author Tarun Tyagi

Number of Sectors of FAT: It must be calculated. The method of calculating the size of FAT has been given in the description of FAT given in the chapter.

The DBR of a FAT32 File System has been given in the figure given next:

Sectors of FAT

Data recovery books

Data recovery books

Data Recovery Book Data recovery books
BPB Publications,
New Delhi, India.
ISBN : 81-7656-922-4
Price : $ 69.00



Sectors Per Track (or Sectors Per Head): Sectors Per Head is the number of sectors grouped under onehead. Likewise, Heads per Cylinder reflects the number of cylinders per head. If this partition is a CHS partition, these values must be the same as those returned by BIOS. If they are not the same, you must consider that the disk has been misconfigured and that the partition may be unusable.

Hidden Sectors: As we have already discussed, this is the number of sectors on the physical disk preceding the start of the volume, before the boot sector itself. It is used during the boot sequence in order to calculate the absolute offset to the root directory and data areas. Think of it as the number of sectors between the beginning of this partition and the partition table itself.

This field should be the same as the "number of sectors preceding the partition" in the partition table. Note that it is not necessarily the physical LBA address of the first sector, as secondary partitions may exist.

If the Hidden Sectors are not the same as in the partition table, you may consider the boot sector as corrupted and the partition unusable. Note also that the high word usually contains garbage in old versions of DOS.

If you suspect that a Boot Sector has become corrupt, you can check several of the fields listed above to see whether the values listed there make sense.

For example, Bytes per Sector will be 512 in the vast majority of cases. You may also expect to see text strings in the executable code section of the boot sector that are appropriate for the operating system that formatted the disk.

For Example, Typical text strings on FAT volumes formatted by MS-DOS include: "Invalid system disk.", "Disk I/O error.", "Replace the disk, and then press any key", "Non-System disk or disk error", "Replace and press any key when ready.” and "Disk Boot failure." Text strings on FAT volumes formatted by Windows NT include: "BOOT: Unable to (or Could not) find NTLDR", "I/O error reading disk." and "Please insert another disk."

But remember that you should not regard this list as being all inclusive. If you find other messages in the boot sector, this does not necessarily indicate that there is a problem with the boot sector. Different versions of MS-DOS and Windows NT may sometimes have slightly different message strings in their boot sectors.

On the other hand, if you find no text whatsoever, or if the text is clearly not related to MS-DOS or Windows NT, you should consider the possibility that your boot sector may have been infected by a virus or that some other form of data corruption may have taken place.

To recover from a boot sector that has been infected by a virus, it is usually best to use a commercial anti-virus program. Many viruses and Trojans will do much more than just write data to the boot sector, so manual repair of the boot sector is not recommended, as it may not completely eliminate the virus or Trojan and in some cases, may do more harm than good. However we are going to deal with DBR in programming section of this book.

If you suspect that the boot sector was damaged for some other reason, it may be possible to recover from boot sector damage without reformatting the drive by manually modifying the fields described above. We shall try to overcome such problems with programming in programming techniques of recovery in this book.

Previous page

page 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20


page 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35

Next page

© Copyright 2002-2005 DataDoctor.Biz

Benefits of online data recovery | Pen Drive Memory Stick Data Recovery Software | Memory Card Data Recovery Software | iPod Data Recovery Software | Digital Camera Data Recovery Software | Removable Media Data Recovery Software | Site Submission Services | Windows Data Recovery Software | FAT Data Recovery Software | NTFS Data Recovery Software | Data Recovery Training | Data Recovery Services | Data Recovery Education Material | Data Recovery Book | Custom Software Development | Offshore Software Development | Microsoft .NET Development | Java / J2EE Development | Wireless / Mobile Application Development | Database Solutions | Website Design | Website Development | Website Promotion | Mobile Website Design | Website Testing | Graphic Design | Data Recovery company India | Data Recovery Canada | Data Recovery United States | Data Recovery United Kingdom | Website Designer Canada | Website Designer United States | Website Designer United Kingdom | Website Designer Outsourcing

Home | Contact us | Downloads | Services | Terms and conditions | Site map

Website Data Recovery | recuperación de Datos | Récupération de données | Datenrettung | Recupero dati | データ復旧 | 데이터 복구 | 数据恢复 | Восстановление данных | De terugwinning van gegevens | Ανάκτηση δεδομένων
Sitemap Site map1 2 3 4 | Spanish1 2 3 | French1 2 3 | German1 2 3 | Italian1 2 3 | Portuguese1 2 3 | Japanese1 2 3 | Korean1 2 3 | Chinese1 2 3 | Russian1 2 3 | Dutch1 2 3 | Greek1 2 3
Data Recovery Book English | Spanish | French | German | Italian | Portuguese | Japanese | Korean | Chinese | Russian | Dutch | Greek