The FDISK MBR (master boot record) is a switch (feature) that can be activated by typing fdisk /mbr at the DOS command prompt. This is an undocumented Microsoft fdisk switch that is used to rewrite the MBR file. The MBR is a very important file stored on the hard drive. The MBR file is also targeted by viruses because it is the first file accessed when the computer is loading the operating system. Once the MBR file is infected the virus copies itself into memory and takes control of the operating system, which makes the virus harder to remove. The MBR can also be corrupted when multi-boot programs are installed.

Caution: You can also remove some multi-boot loaders by using this switch, which will prevent you from accessing some multi-boot systems.

Fdisk MBR Switch

To use this MBR switch you need to boot from DOS using either a floppy, hard drive DOS partition, or a CD with DOS. Once DOS is started you can start fdisk mbr by typing at the prompt fdisk /mbr.  The command will write a new MBR file to the first sector, 512 bytes, on the hard disk. 

Fdisk

Fdisk can also be used to partition a hard drive so that you can have a partition for storing important files or images outside of the operating system.  I have another HubPage on Fdisk that will take you step by step if you want to setup a partition on your hard drive where you can install DOS. I also have a YouTube video that can help you to get familiar with Fdisk.

Some other Hub Pages that you might find useful:

FIXMBR Windows XP Fdisk /MBR Tool The FIXMBR recovery console command for Windows XP does the same that Fdisk /MBR dose for DOS.

FDISK DOS Partition Utility Tutorial Fdisk is a Microsoft DOS utility for partitioning hard drives. You should have a partition for important data and operating system backup images. Backup images will allow you to restore your system quickly.

Computer Repair Tools - Great Free Software Some of the best computer repair tools are free and open source software. These great tools are better than some of their commercial counterparts.

GParted - Great Open Source Hard Drive Partition Utility GParted is a great open source partitioning utility that is fast and easy to use. You can even run GParted from a Linux Live CD.

Installing Windows XP From the i386 Folder or Flash Drive Installing Windows XP is something everyone will need to do from time to time. Windows will get slower because it is not a self tuning or self maintaining operating system so in time it will slow down and die.