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Posted 11 Jan 2004


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Changing volume's serial number

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4 Mar 20043 min read
An article showing how to change drive's serial number


This article will demonstrate how to change the drive's serial number on three different file systems: FAT, FAT32 and NTFS. The article's source code files come with a home made DiskSector read/write class for WinNt/2k/XP and Win9x system. The article also comes with a handy dialog based application that allows you change the serial number visually.

How it works

Usually, the serial number of a drive is generated every time you format your hard drive and there is no documented way to change it afterwards.

It is worthwhile noting that the serial number returned by the "dir" command or the GetVolumeInformation() API is not the hardware serial number that comes from the manufacturer, instead this serial number is assigned and stored in the hard drive (mostly in the boot sector) by the file system and *can* be changed by software.

Knowing that the serial number is stored in the hard drive, I started looking up information about the three different file systems: FAT, FAT32, NTFS. The most relevant part to look at was the boot sector format of each of the different file systems. Usually, the bootsector holds vital data for the integrity and the operation of the file system.

Among these fields, we list this table with the fields names, file system and the corresponding offset (in hex) of the field in the boot sector:

Table 1

Volume Label 0x2B0x47?
File system ID0x360x520x3
Serial number0x270x430x48

For example, we can read an entry of this table as: "In the FAT file system, the 'Serial Number' is stored at offset 0x27 starting from the boot sector origin". It is important to know that the boot sector starts at sector zero and is 512 bytes long. The next part will explain how the ChangeSerialNumber() function can be written.

Explaining the code

First, I will explain the code flow:

  1. Open the hard drive device in order to read/write sectors.
  2. Read the boot sector
  3. Identify the file system of the drive in question
  4. Modify the serial number field according to the current file system (refer to table 1)
  5. Write back the modified boot sector
  6. Close the hard drive device
void CVolumeSerialDlg::ChangeSerialNumber(DWORD Drive, const DWORD newSerial)
  const max_pbsi = 3;

  struct partial_boot_sector_info
    LPSTR Fs; // file system name
    DWORD FsOffs; // offset of file system name in the boot sector
    DWORD SerialOffs; // offset of the serialnumber in the boot sector

  partial_boot_sector_info pbsi[max_pbsi] =
   {"FAT32", 0x52, 0x43},
   {"FAT",   0x36, 0x27},
   {"NTFS",  0x03, 0x48}

  TCHAR szDrive[12];

  char Sector[512];

  DWORD i;

  sprintf(szDrive, "%c:\\", Drive & 0xFF);

  if (!disk.Open(szDrive))
    ShowErrorString("Could not open disk!");

  // read sector
  if (!disk.ReadSector(0, Sector))
    ShowErrorString("Could not read sector!");

  // try to search for a valid boot sector
  for (i=0;i<max_pbsi;i++)
    if (strncmp(pbsi[i].Fs, Sector+pbsi[i].FsOffs, strlen(pbsi[i].Fs)) == 0)
      // we found a valid signature

  if (i >= max_pbsi)
    MessageBox(_T("Cannot change serial number of this file system!"),
       _T("Error"), MB_ICONERROR);
  // patch serial number
  *(PDWORD)(Sector+pbsi[i].SerialOffs) = newSerial;

  // write boot sector
  if (!disk.WriteSector(0, Sector))
    ShowErrorString("Could not write sector!");

  ShowErrorString("Volume serial number changed successfully!\r"
        "You might want to restart your system for changes to take effect!");

The core of this function is the 'partial_boot_sector_info/pbsi' table which is built from Table 1. This table will allow us to check what file system this boot sector belongs to and then it allows us to correctly patch the serial number field. It appears that if you change the serial number of an NTFS volume, changes won't take effect until you restart your system.

Also note that changing the partition's serial number will render some licensed programs useless, therefore write down the original serial number before attempting to changing it, just in case you wanted to restore it back.



  • v1.0
    • Initial version: only WinNT support
  • v1.2
    • Win9x and WinNT support added
    • Documented updated


This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

A list of licenses authors might use can be found here


About the Author

Elias Bachaalany
Web Developer
United States United States
Elias (aka lallousx86, @0xeb) has always been interested in the making of things and their inner workings.

His computer interests include system programming, reverse engineering, writing libraries, tutorials and articles.

In his free time, and apart from researching, his favorite reading topics include: dreams, metaphysics, philosophy, psychology and any other human/mystical science.

Former employee of Microsoft and Hex-Rays (the creators of IDA Pro), was responsible about many debugger plugins, IDAPython project ownership and what not.

Elias currently works as an Anticheat engineer in Blizzard Entertainment.

Elias co-authored 2 books and authored one book:

- Practical Reverse Engineering
- The Antivirus Hacker's Handbook
- The Art of Batch Files Programming

Comments and Discussions

QuestionI wanna open your source files in MS Visual Studio to learn about it Pin
yvon-3121-Apr-21 22:00
Memberyvon-3121-Apr-21 22:00 
QuestionUsable with SD / Thumb drives? Pin
Member 126202749-Apr-21 13:58
MemberMember 126202749-Apr-21 13:58 
Questioncount files in usb driver (Fat32 formated) Pin
hamed_babaee29-Nov-16 2:26
Memberhamed_babaee29-Nov-16 2:26 
QuestionAnd how we can read another special sector? [modified] Pin
Abolfazl Ghavidel16-Nov-10 19:53
MemberAbolfazl Ghavidel16-Nov-10 19:53 
GeneralWorks great - thanks Pin
Andy Mascord11-Sep-10 12:04
MemberAndy Mascord11-Sep-10 12:04 
GeneralError on Vista Pin
darrelki6-Aug-09 22:56
Memberdarrelki6-Aug-09 22:56 
GeneralVolume Serial Number Demo Pin
liverwort460027-Jan-09 3:55
Memberliverwort460027-Jan-09 3:55 
QuestionExcellent Job Pin
ssa-ed22-Jan-09 14:45
Memberssa-ed22-Jan-09 14:45 
Generalthanks Pin
boo-mmx13-Oct-08 8:40
Memberboo-mmx13-Oct-08 8:40 
GeneralWindows Vista Pin
Cleiton A.27-Jan-07 19:24
MemberCleiton A.27-Jan-07 19:24 
GeneralRe: Windows Vista Pin
RP232-Mar-07 3:14
MemberRP232-Mar-07 3:14 
GeneralDisk Partition Table Pin
Sana Nazimuddin Qureshi19-Dec-05 19:19
MemberSana Nazimuddin Qureshi19-Dec-05 19:19 
GeneralRe: Disk Partition Table Pin
Elias Bachaalany19-Dec-05 20:17
MemberElias Bachaalany19-Dec-05 20:17 
GeneralRe: Disk Partition Table Pin
Steevej14-Jun-07 7:35
MemberSteevej14-Jun-07 7:35 
QuestionHow to get manufacturer's ID of the hard disk? Pin
Habeeballah16-Dec-05 21:27
MemberHabeeballah16-Dec-05 21:27 
AnswerRe: How to get manufacturer's ID of the hard disk? Pin
Elias Bachaalany18-Dec-05 20:15
MemberElias Bachaalany18-Dec-05 20:15 
AnswerRe: How to get manufacturer's ID of the hard disk? Pin
philbnt6-Oct-06 1:58
Memberphilbnt6-Oct-06 1:58 
GeneralRe: How to get manufacturer's ID of the hard disk? Pin
Douglas R. Keesler29-Dec-06 22:50
MemberDouglas R. Keesler29-Dec-06 22:50 
GeneralRe: How to get manufacturer's ID of the hard disk? Pin
member 104177015-Mar-07 20:39
Membermember 104177015-Mar-07 20:39 
Generaldead Hd serial recovery Pin
scatterlancer25-Sep-05 4:33
Memberscatterlancer25-Sep-05 4:33 
GeneralRe: dead Hd serial recovery Pin
Elias Bachaalany27-Sep-05 21:56
MemberElias Bachaalany27-Sep-05 21:56 
GeneralQuestion on VSN byte order Pin
PiotrGutkowski29-Jun-05 9:44
MemberPiotrGutkowski29-Jun-05 9:44 
GeneralRe: Question on VSN byte order Pin
Elias Bachaalany30-Jun-05 21:06
MemberElias Bachaalany30-Jun-05 21:06 
GeneralRe: Question on VSN byte order Pin
PiotrGutkowski1-Jul-05 4:01
MemberPiotrGutkowski1-Jul-05 4:01 
Generalhelp me Pin
ertaneren30-May-05 7:30
Memberertaneren30-May-05 7:30 

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