How to Use the Fdisk from Microsoft

Even though the most effective means to create and delete partitions in HDs, the command fdisk is used even today, since it is possible to use it from a simple boot floppy (startup), usually to Windows 98. This tutorial shows what is partition and how to use the features of fdisk to create one or more.

What is the partition

Assume that you have a hard disk drive (HDD) with 40 GB of capacity. It is possible to divide this space into it seems that there are more HDs on the computer. For example, you you can split that HD into two parts, being that a receives 15 GB and the other, 25 GB. The machine still have only one HD, but the system operating appears that there are two: one with a 15 GB and the other with 25 GB. Each part is known as partition.

Before proceeding, it is necessary for you to understand what is “primary partition” and “partition extended”:

Primary partition: basically, this type partition serves to install operating systems. Thus, to install the Windows, for example, it is necessary to make use of a primary partition. On a HD you can have,a maximum of 4 partitions of this type;

Extended partition: the partitions primary may not be subdivided. Soon, you should use a partition extended if it is necessary to create other. The partitions extended make use of the free space on the disk. A partition extended can be divided. For this, it is necessary that each division “win” a logical unit, this is, will be represented by a letter (D:\, E:\, etc). In this type of partition it is not possible to install operating systems.

Entering the fdisk

Fdisk is a program that does not run if Windows is loaded, therefore, it is necessary to use a floppy disk or a Boot CD that contains it. You can use tools own to create boot disks, or use Windows 98: goto the Control Panel and in Add/Remove Programs, choose the tab Startup disk. Put an empty floppy in the drive A:\ and click Create Disk. In a short time the boot disk will be created. Then just restart the computer with the floppy disk in the drive and make sure that the machine is booted by this means. For so, as soon as the PC is switched on, press the Delete button (or equivalent) repeatedly until the Setup is loaded. In it, change the boot options so that the floppy disk be the first to be read. Refer to the manual of your motherboard for more details about this procedure.

It is also possible to use fdisk from the CD installation of Windows 98. For this, it is necessary to boot with this CD, and as in the case of the floppy disk, the Setup has to be configured to read CDs to boot.

When the boot start, is by floppy disk, by the CD, the system it will list some options. You can choose”Start with CD-ROM support”. If you choose the option “Without support”, the CD-ROM cannot be used.

The choice has been made, in a few moments the boot will be complete and a letter corresponding to the floppy or to the CD will appear then a blinking cursor. This indicates that you can already type the fdisk command. Do this and press Enter on your keyboard.

First of all, a warning will appear saying that the “disk has more than 512 MB and that this version of Windows includes support for advanced for large disks (…)”. At the end of this notice, the the system asks if you want to “enable the drive support large capacity”. Confirm by pressing the s key on your keyboard and pressing Enter then.

  1. Create a partition or logical drive OF
    2. Set a partition active
    3. Delete a partition or logical drive OF
    4. View information about the partitions

You must enter the number of the option the desired (1, 2, 3 or 4) and press Enter.

The following is a description of each option:

Option 1: is used to create a partition;
Option 2: is used to define a partition active. When a boot is given, the computer looks in the partition active the operating system;
Option 3: is used to delete partitions;
Option 4: is used to list the information referring to the existing partitions.

Creating partitions

When you choose option 1 on the main screen of fdisk, a menu will come with 3 items:

  1. Create a primary DOS partition
    2. Create an extended DOS partition
    3. Create logical drives in the extended partition of the OF

If the HD does not have anything recorded, it is necessary to create first a primary partition, therefore, you you should choose option 1. If you already has a primary partition, choose the option2 to create extended partitions. If you already you have extended partitions, you must assign a drive logic to it, otherwise the operating system not the see. For this, choose the item 3.

Note: when fdisk cites partition primary or extended DOS, means that the program will assign the file system to FAT to the partition.

When you choose option 1 or option 2, on the screen, you can set the size of the partition. You can indicate the desired size in MB or in percentage. Fdisk certainly it will ask you if you want the partition to manage 100% of the disk. Choose “No”, otherwise, the partition will take up all of the HD, not allowing the creation of the other.

When you choose the option 3, the fdisk will show the partitions existing extended, and then you can choose in which to assign a logical drive.

The partitions are created, they can only be used after formatted (this should be done after a reboot). During your installation, the operating systems checarão if there is formatting. If not, they will carry out this procedure.

On the main screen of fdisk, you should choose the option 2 (Set active partition), if there is no in this condition. A partition non-active it may not be used for the installation of an operating system. Only primary partitions can receive the parameter of active.

Deleting a partition

On the main screen of fdisk, you should choose the option 3 (Delete a partition or logical drive DOS) if you want to delete a partition. After this, the following list will appear:

  1. To delete a primary DOS partition
    2. To delete an extended DOS partition
    3. To delete logical drives in the extended partition of the OF the
    4. To delete a non-DOS partition

Options 1 and 2 are self-explanatory. The option 3 serves to delete a logical drive in the partition extended. For example, suppose you have two logical drives a partition (if there are two partitions).You can delete a and thus the partition you will be left with only one logical drive.

Option 4 works with partitions, non-DOs, for example, partitions used by the Linux operating system.

In choosing any of these options, the fdisk will show a list of the partitions that may be deleted. Just choose the desired and press Enter on your keyboard. The program will prompt for confirmation before performing the procedure.

Important: when you delete partitions, all the data recorded on the HD will be lost!

Fdisk for hard Drives over 64 GB

In a test conducted for a tutorial of the DigoPaul, we try to use the fdisk on a HD with 80 GB. However, the program acted so strange.

Searching for the problem, we discovered that the fdisk does not work with Drives larger than 64 GB. On the Microsoft website, it appears that when a HD with more than 64 GB is submitted to fdisk, the program points to the the size of the HD by subtracting the 64 GB. For example, if the HD has 80 GB, fdisk it states that it has 16 GB (80 GB – 64 GB).

According to Microsoft, this problem occurs because fdisk uses some 16-bit values to calculate the size of a disk. With HDs with more 64 GB, there is an overflow of memory, and the fdisk happens to work in an incorrect manner.

When Windows 98 was released, the HDs is more common in the market had up to 10 GB. When Windows 2000 came about, the standard was 20 GB. As hard Drives with more capacity are available currently, it is not rare to find situations where these disks have installed the Windows 98. The problem begins the fact that Windows 98 was released in a time in which Hard drives with many GB were rare and used in special machines. Therefore, at that time, no one had to worry about HDs with more than 64 GB, because they were virtually non-existent. With the emergence hard disks with this characteristic, it is that the problem with the fdisk was noticed.

Fortunately, this problem has a solution. Microsoft has released an update of fdisk that allows you to work with HDs with more than 64 GB. However, the company stresses that this fix should only be used in the case of the emergence of the problem pointed out previously. In addition, this solution does not work for HDs is working in mode LBA (Logical Block Addressing) and for disks more than 137 GB capacity.

The command fdisk /mbr

When fdisk is used to set partitions, use a table, called the “partition table”, that indicates how is the division of the HD, or is, where is the primary partition, the extended partition, etc. This table is located in the first sector of the first track of the HD (the well-known “track zero”). This area is known as MBR (Master Boot Record).

The MBR contains a small program called a “boot loader”. When a boot manager is installed on the computer (a program that allows the user to choose which operating system to use, if there is more than one on the machine, for example, Linux and Windows) the boot loader is changed or replaced. If you want to take this manager and make the computer give boot direct by Windows, you must type the following command at the DOS prompt:

fdisk /mbr

This command, basically, it restores the information from the MBR and configure it to work with Windows. Its use is also useful in situations where the virus destroys the MBR.

Note: Microsoft recommends that this command not to be used on Drives with more than 4 partitions.


Although there are tools much more efficient to work with the partitions of a HD, back and half-fdisk ends up being used. For example, in a situation where there is no other software of the type available. This has happened here in DigoPaul. Therefore, it is important to know how to fdisk works.

How to Use the Fdisk from Microsoft 1

How to Use the Fdisk from Microsoft
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