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Asked: 2026-05-17T00:24:36+00:00

I need to clear sector 0 for removable media devices (custom USB memory devices)

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I need to clear sector 0 for removable media devices (custom USB memory devices) which I have been trying to clear within a WPF/C# application. My first attempt was to use DD, but I ran into problems. During the manufacturing of the devices a MBR is created at sector 0 and the volume (logical?) starts at sector 40. When I issue the following command it clears sector 40 and not sector 0:

dd bs=512 count=1 if=/dev/zero of=\.\E:

I found another version of DD here which includes a wipe utility. I tried this version and I am seeing the same behavior. I am using both HxD and Runtime’s DiskExplorer that sector 40 is being cleared and not sector 0. I could use HxD or Runtime’s DiskExplorer, but this needs to be scriptable.

Does anyone know of any other methods of clearing (filling) sector 0 within Windows XP SP2?? Any help would be greatly appreciated. Thanks.

Mark



Solution: My solution used WMI to find the physical drive based upon the logical drive letter. First, query the Win32_LogicalDiskToPartition class to find the logical drive I am looking for. This provides the Antecedent field which constains something like ‘…DeviceID=”Disk #X, Partition #Y”‘. Next, I query Win32_DiskDriveToDiskPartition class while searching against the Dependent field to find the match for the Antecedent field within the Win32_LogicalDiskToPartition class. Once found, the Antecedent field from Win32_LogicalDiskToPartition will yield the physical drive. I selected atzz since it is the closes to my solution. I wanted to use Eugene’s suggestion, but I only had a few hours to implement this so I selected the easier of the two. I will need to revisit this at a later time though.

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1 Answer

  1. Editorial Team

    There are two ways to format a USB drive, from Windows standpoint:

    • As a floppy disk. In this case entire USB drive contains a single file system, and its boot record is located in sector 0.

    • As a hard drive. In this case, sector 0 contains MBR with partition table. Actual file system(s) with their individual boot records are located further on the drive.

    I think you are observing the second case. Using \.\E: to identify the device, you end up accessing file system’s boot record instead of MBR.

    Here is how you can access sector 0 of the USB drive.

    1. Load WinObj from here.
    2. In WinObj, under GLOBAL??, find E:. It will be a SymbolicLink pointing to something like \Device\Harddisk2\DP(1)0-0+30.
    3. Under GLOBAL??, find a PhysicalDrive# symlink referring to the same Harddisk# that you found on step 2. Most probably it will have the same numeric suffix as Harddisk#. E.g.: SymbolicLink PhysicalDrive2 refers to \Device\Harddisk2\DR47.

    4. Use the PhysicalDrive# you’ve found in DD command:

      dd bs=512 count=1 if=\\.\PhysicalDrive2 of=mbr.dat

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