When you turn on your PC, the processor attempts to begin the process of processing data. But, since the system memory is empty, the processor doesn’t really have anything to execute, or even begin to know where to look for it. To ensure that the PC will always boot regardless of the BIOS code, both chip and BIOS manufacturers developed their code so that the processor once turned on, always starts executing at the same place, FFFF0h.  Every hard disk must have a consistent “starting point” where key information is stored about the disk, such as the number of partitions and what type they are. There also must be someplace where the BIOS can load the initial boot program that starts the process of loading the operating system. The place where this information is stored is called the master boot record (MBR).

When a computer starts and the BIOS boots the machine, it will always look at this first sector for instructions and information on how to proceed with the boot process and load the operating system. The master boot record contains the following structures:


Master Partition Table: This small table contains the descriptions of the partitions that are contained on the hard disk. There is only room in the master partition table for the information describing four partitions. Therefore, a hard disk can have only four true partitions, also called primary partitions. Any additional partitions are logical partitions that are linked to one of the primary partitions. One of the partitions is marked as active, indicating that it is the one that the computer should use for booting up.


Master Boot Code: The master boot record contains the small initial boot program that the BIOS loads and executes to start the boot process. This program eventually transfers control to the boot program stored on whichever partition is used for booting the PC

Now days most people I have seen going for windows 7. So no wonder I am going to talk about fixing MBR in widows 7. Follow these following steps to fix your PC problem.

First of fall If you do have a Windows 7 Installation DVD its will be easier or if you don’t have you can alternatively use a Windows 7 System Recovery Disc. Now turn your computer on, booting from either your Windows 7 Installation DVD or Windows 7 System Recovery Disc.  After the installation or recovery disc loads, if prompted, select your language settings and then continue.  If you are using the installation DVD, when prompted by the following screen select Repair your computer.

Now after pressing repair button the computer will take a moment now to scan itself for any Windows installations, after which you will probably, be given a choice to select which installation you wish to repair.  Continue by selecting the suitable Windows installation from the list. Now you will see system recovery option screen. Here you will see some list of choices that can help you in repairing your operating system. Select the Startup Repair to let the pc fix the problem automatically. Now all those problems related to startup is fixed.
The master boot record is a “vulnerable spot exploited by viruses” due to its necessity of system booting. If your computer is compromised due to virus, then it’s necessary to run a MBR anti-virus check on the system before taking any further steps.

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