This post mainly tells how to fix MBR in Windows 8 using MiniTool Partition Wizard if the operating system fails to boot and reports "Missing operating system"…If you are also troubled by how to fix MBR Windows 8, try the solution here.

What Is MBR

MBR is the master boot record of a hard disk. It is created on the first partition when you first install Windows. MBR consists of three parts, i.e. Boot Loader, Partition Table and Magic Number. Boot loader is a program that loads an operating system when a computer is turned on. Partition table records partition information on local disks. Magic number(0xAA55/0x55AA) marks the device as a valid bootable media. An invalid magic number indicates a corrupted or missing MBR. Master Boot Sector contains 512 bytes in total, of which the boot loader takes up 446 bytes, partition table 64 bytes, and magic number 2 bytes. If the MBR is damaged, you won’t be able to boot into Windows. 

MBR construction

Necessity to Repair MBR in Windows 8

Why fix MBR in Windows 8? Obviously, this is due to MBR damage. And this damaged can be caused by virus attack, power outage and improper operations like listed below: 

Being unwilling to use Ubuntu any more, I deleted the partition that contains the system. but it deleted GRUB at the same time, and now my computer cannot boot into Windows 8. I looked online and was suggested to fix MBR with Windows 8 disc. Nevertheless, I do not have such a disc. What should I do?

As we have mentioned, if the master boot record is broken, your computer will fail to boot and show you some of the following errors: 

  1. “Error loading operating system­_”
  2. “Operating System not found_” or “Operating System missing_”
  3. “Invalid partition table_”
  4. “Reboot and Select proper Boot device or Insert Boot Media in selected Boot device and press a key_” 

In this situation, you have to roll up your sleeve and find a way to fix MBR in Windows 8. 

Click here if you’re interested in how to get files off a broken computer. 

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Two Ways to Fix MBR in Windows 8

Normally, there are two ways to repair MBR. Follow the instructions below to repair master boot record by yourself. 

1. Fix MBR with command prompt and installation DVD 

Fix MBR with command prompt requires the original Windows 8 or 8.1 installation DVD. The instructions are:
1. Boot from the original installation DVD.
2. At the Welcome screen, click Repair your computer

repair your computer

3. Choose “Troubleshoot > Advanced options > Command Prompt”. 

process of command prompt4. When the Command Prompt loads, type the following commands in order: “bootrec /FixMbr > bootrec /FixBoot > bootrec /ScanOs > bootrec /RebuildBcd”. Remember to press “Enter” after each command and wait for each operation to finish.

5. Remove the DVD from the disk tray.

6. Type exit and Hit “Enter”.

7. Restart your computer and check if Windows 8/8.1 can boot now. 

Here is the instruction of how to fix MBR in Windows 8 with command promptClick to Tweet

2. Fix MBR without CD

Another feasible method is by using third-party software to repair MBR without CD. Currently, There is lots of partition software in the market that can achieve this goal, and MiniTool Partition Wizard Bootable CD is among the most reliable ones. In addition, no professional knowledge is required, and only three steps are needed. Next, we will show users the detailed steps. 

MiniTool Partition Wizard Bootable CD Helps to Fix MBR in Windows 8 without CD

MiniTool Partition Wizard Bootable CD is the bootable edition of MiniTool Partition Wizard generated by MiniTool Bootable Media Builder, which is a paid feature embedded in each paid edition of MiniTool Partition Wizard, such as the Pro Edition. So first of all, you need to get a paid edition to unlock Bootable Media Builder feature. 

Step 1: Users need to create a bootable CD/DVD/USB drive with Bootable Media Builder feature. After that, connect boot flash drive with computer to start the very computer.

ReferenceHow to Build Boot CD/DVD Discs and Boot Flash Drive with Bootable Media Builder?

Step 2: Set computer to boot from the bootable media. Press “+” “-” to move the target bootable media to the first place and then press F10 to save settings. 

change boot order

Step 3: Soon you will see the following interface. You should select “MiniTool Boot Disc” to go on.

windows boot manager

Step 4: After successful boot, users will see the main window of MiniTool PE Loader, where you can enter MiniTool Partition Wizard Bootable CD. 

WinPE loader

Step 5: To fix MBR for Windows 8, users need to select the target disk and choose the function Rebuild MBR. At last, click on the icon Apply to execute changes. 

 rebuild MBR

apply the operation

After these operations, we can say the work to repair MBR in Windows 8 is finished. Now you can remove the bootable media and set your computer to boot from the system disk. 

Here is the instruction of how to fix MBR in Windows 8 without CD–Click to Tweet


In a word, MBR damage can cause system boot failure. If you are prompted or need to fix MBR Windows 10, 8, 7, Vista, XP, and even Windows Server, turn to the partition tool – MiniTool Partition Wizard. We believe it can meet most users’ demands. 

If you have any good idea about accidentally deleted partition recovery, you can share with us. We would appreciate it if you leave any suggestion or comment by sending an email to [email protected].

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