Low-Level Formatting


By George Snell

SCSI Drives    IDE Drives    Before Formatting    BIOS Utilities    Software Utilities    Drives by Manufacturer

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CAUTION: Low-Level Formatting your Hard Drive will permanently remove all Data from the Drive. It will be in the same condition as when received from the factory. Back up all Data, and check the Re-installing Windows section for notes on a complete re-install of an operating system, to ensure you have all necessary programs, drivers and other material at hand before continuing.   Please also see the Note at the bottom of this page.

Virtually the only two types of hard drives in use today are IDE (Integrated Drive Electronics) and SCSI (Small Computer System Interface). Most home and business computers utilize the IDE type hard drive, due to low initial cost and wide availability. Most servers and a few high-end desktop workstations will use SCSI hard drives. Custom or home built systems may have any either or both types depending on the budget of the builder, or, more likely, what parts were available at the time the unit was built.

UPDATE: Since most utilities listed here have been removed from the manufacturers' websites, we have made them available here on ours. If you need to download any of the utilities discussed in this article, just click on the provided link and save to your local directory. We are still offering information about Quantum drives, even though Quantum is no longer offering support. I have an email link available to assist in resolving any questions about formatting your hard drive. If you have a make not covered here, drop me a note, I'll get back to you as quickly as time permits. All mention of Ontrack software is only by personal preference. Any links to Ontrack software will take you directly to their website for more information, as their products are for sale, and, as far as I know, they have no free software for formatting or installing hard drives. Manufacturers of hard drives often offer a free, customized version only for use with their products. Be sure to check the website of the manufacturer of your hard drive for more information.

Why would you want to do a low-level format on a modern hard drive? The main reasons are virus infection and development of bad sectors. For security purposes, you would want to take another direction, as there are any number of programs that will recover data from a formatted hard drive. Check the freeware and shareware sites for some excellent tools for securely deleting files. My favorite has been BC-Wipe, which was a freeware program. I understand it is no longer freeware, and they are only supporting purchased versions. I'll let you know when I find a new one I like, one that works with FAT, FAT32 and NTFS file systems. 

At then end of this paper, I will offer a few suggestions as to how to avoid the problems encountered attempting to low-level format IDE hard drives, and why I would recommend not doing a low-level format on these drives. SCSI drives are covered first, since you have little option in low-level formatting. You either have the proper utilities, with instructions, or don't do it. Simple.


If you have SCSI (pronounced "scuzzy") hard drives you want to low-level format, you must have the utilities provided by the manufacturer of your SCSI controller. These may be built into the controller, or furnished as separate software. This is the only way to safely low-level format a SCSI drive. If you use the wrong utility, you may find it very difficult to get your hard drive back to a useful condition.

There are many manufacturers of SCSI controllers. By far the most popular is Adaptec. They have many utilities available for download to assist you in your endeavors to reformat your SCSI hard drive. You will find updates to any software furnished with your controller, as well as access to all the utilities they have available.

Another popular manufacturer of SCSI controllers is Tekram Technology. They have a great search engine that will take you immediately to the help for your specific controller, along with many other products they manufacture.

If you have a controller card you cannot identify, or, after following all instructions included with any software you download you still have problems, you can email me at gsnell for assistance. If there is enough interest in this subject, more in-depth information regarding SCSI devices will eventually be posted here.


IDE hard drives can only be properly low-level formatted at the factory. All IDE drives have control information on track 0 or -1 that only the controller can read. This information includes bad track information, head skew factors and zone sector information. Fortunately, all newer hard drives only operate in a translation mode, so we can successfully do a format that could be more properly called a mid-level format. I don't know of any virus that can infect the low-level format installed by the manufacturer.

The reason for this is twofold:

  1. All hard drives are initially formatted in native mode, and all, except the oldest IDE drives, operate in translation mode. The special tracks containing information specifically for the controller cannot be accessed in translation mode. Even if you could access this information, the BIOS and operating system would not be able to read the hard drive, as they cannot handle Zoned Bit Recording. (See Software Utilities below for more on Zoned Bit Recording)
  2. All computer viruses are programs. They may be Java script, Word Macros, or machine language. They must be run on top of the operating system. The operating system cannot access your IDE hard drives, except when the drives are in translation mode.

Some manufacturers provide utilities to properly do what is referred to as a low-level format. For those that do not, other utilities, such as Ontrack's Disk Manager, are available. (Further links where possible, and recommendations to other programs as necessary are provided below).

IDE hard drives are broken down into several groups. Early IDE drives used the same control interface commands as the forerunner MFM, RLL and ESDI drives. The main advantage came from having the controller mounted on the hard drive, as opposed to on a card mounted in a slot on the motherboard. This freed the design engineers from having to conform to interface standards between the hard drive and controller, since the controller would never be used with another drive. Later hard drives conform to various ATA (AT Attachment) standards, which specify various additional commands and other features found on the modern IDE hard drive.

A few words about IDE controller cards are in order. The earlier separate cards are not controllers, only interface cards with buffers to prevent damage to the drive or motherboard due to stray electric impulse. The controllers mounted on the motherboard are, for the most part, nothing more than a stripped down ISA slot, with a 40 pin subset of the 98 pins available on a standard 16-bit ISA slot. An IDE connector only requires one IRQ, plus the required signal pins. All IDE and EIDE interfaces are a 16-bit bus. 32-bit disk access is accomplished 16 bits at a time. The reason for this is that, even with 2 hard drives hooked to the same controller using 32-bit disk access, the bus can handle the data faster than both hard drives working simultaneously can send data.

Enough of trivia. Time to get to the hard core facts of getting that drive formatted.


If you have a stubborn virus or are just beginning to develop some bad sectors on your hard drive, I recommend that you try this formatting routine before going further. The steps are easy, and, unless you have a very stubborn problem, these routines will correct any problems you are having with your hard drive.

  1. Be sure you have all programs, drivers and other material at hand to restore your hard drive.
  2. If possible, back up all the important data on your hard drive. Don't forget address books and Internet bookmarks.
  3. Boot up from the floppy drive with a known good boot disk. This can be Disk 1 of MS-DOS, or your Windows 95 or Windows 98 emergency boot disk. Any drive over 2 gig should be prepared using a Windows 95 OSR@ or Windows 98 boot disk. (Don't worry if you are using Windows ME, Windows NT, Windows 2000 or Windows XP. A Windows 98 boot disk can be used to remove the partitions and install a container that will allow you to reinstall your version of Windows. For the purist, remember that we are talking about reformatting, and wiping out all data currently on the drive, anyway.)
  4. When you get to the A:> prompt, run FDISK. Type   FDISK   and press Enter.
  5. Remove all partitions in the following order:
    1. All assigned drives in extended partitions
    2. Any extended partitions
    3. The primary partition
  6. Exit FDISK, and reboot the computer with the reset button or Ctrl-Alt-Del keys.
  7. When you are back to the A:> prompt, type in exactly the following:
    Check to be certain the command looks exactly like the above. NO SPACES! When you are sure the command is typed correctly, press the Enter (Return) Key.
  8. The screen may or may not blink, and should return an A:> prompt. No other message will appear.
  9. You have now written a new Master Boot Record to your hard drive, and have overwritten any virus hidden in the master boot record.
  10. Reboot your computer.
  11. Run FDISK. If using Windows 95B or higher, or Windows 98, you can choose to use FAT-32 large drive partitions. Choose option 1 to create a primary dos partition, then create extended partitions and drives, if you want or need to.
  12. Exit FDISK and reboot the computer.
  13. From the A:> prompt, type   FORMAT C:   and press Enter. If you want to have the disk bootable, the command is   FORMAT C: /S   to format and transfer the operating system.

You have now removed any virus that resided in your Master Boot Sector or Boot Sector. You have also replaced any damaged FAT tables, and mapped out any bad sectors to prevent them from being used by the operating system or any programs. Use normal procedures to install your operating system and programs.


Of the various methods to format an IDE hard drive, the easiest is with the 527 Mb and smaller non-intelligent IDE hard drives, on an x486 computer. Many of the earlier Award Bios chipsets had a low-level format utility built into the CMOS. All you have to do to format these hard drives is to press the <Del> key while booting the computer, and choose hard drive utilities from the menu. After running the format utility, reboot with a DOS floppy, run FDISK to partition the hard drive, then do a standard DOS format. This utility appears no longer to be available on newer computers, due to the introduction of hard drives larger than 527 Mb. The only thing to really remember using the Award Bios format is that it usually recommends an interleave of 3. This needs to be changed to 1, as all IDE hard drives use an interleave of 1. The only possible damage to these drives when doing a low-level format is overwriting the bad-track map, and possible alteration of skew factors.

If a large hard drive is accidentally formatted using this utility, any damage can be undone with programs such as Ontrack's Disk Manager, PC-Technician by Windsor Technology and Micro-2000's Microscope. Free, manufacturer-specific versions of Disk Manager or EZ-Drive are available from your drive manufacturer. If you have trouble using these utilities, check the links below for more instructions.


New hard drives all use what is called Zoned Bit Recording - ZBR. Early MFM drives had 17 sectors per track, RLL drives 26 sectors per track and ESDI drives had 30 to 80 sectors per track. Early IDE drives varied considerably from model to model. With Zoned Bit Recording, the number of sectors per track varies. The inner tracks, or cylinders, will have fewer sectors. As you travel towards the outer edge of the disk, more surface is available per track, so sectors are added to take advantage of the extra space. There may be 15 or more zones on a hard drive, ranging from 100 or so sectors per track on the inner tracks to 230 or more on the outer tracks. An interesting note is that the newer hard drives transfer data substantially faster from the outer rings than they do from the inner tracks.

Operating systems cannot handle Zoned Bit Recording. Therefore, all newer IDE hard drives use translation mode so that the BIOS and operating system can access them. This is what allows us to safely low-level format an IDE hard drive. When low-level formatting is done in translation mode, track 0 cannot be overwritten, preserving the bad track map, and all other information the controller needs to properly communicate with the hard drive.


As each manufacturer handles Low-Level Formatting differently, specific instructions are provided on the following pages. Choose the one for your drive:

Maxtor Drives    Quantum Drives    Western Digital Drives    Seagate Drives

Please Note
Some Manufacturers of Hard Drives state that attempting to properly Low-Level Format your Hard Drive will void any existing manufacturer's warranty, and recommend that Hard Drives be returned to tne manufacturer for any required Low-Level Formatting.
Any attempt to Low-Level Format a Hard Drive is done so at your own risk, therefore. Neither the author nor any other contributor to this site can accept any responsibility for any damage to your Hard Drive or Data should you decide to use any information made available in this article.

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George Snell 1999-2002