All About the BootMGR and various BootMGR related Issues

Introduction

Hi, I will be talking about the infamous Windows boot manager in this tutorial. To start, I'll give a concise, but detailed explanation of what bootmgr does. I will follow it up with various issues that can cause Windows not to boot and try to give you ways to fix it.



Windows Boot Manager

Whenever the OS is installed, you can choose to let Windows partition itself or you can manually partition your drive. Generally, it's recommended to let Windows do it unless you are an experienced user with different needs. Windows creates a system reserved partition where it loads all of the OS dependent files. On Vista, Windows uses the winload.exe file to boot. On all versions after Vista, Windows uses BCD which replaces boot.ini file used in Windows XP and earlier. All of these files will be found on the system reserved partition. So what does all this mean exactly? Windows uses its own boot loader which can easily become corrupted.


Commonly Seen Error Messages



Common Issues Related to bootmgr

• 
  ■ Corrupt boot sector or files
  ■ Corrupt master boot record (MBR)
  ■ Misconfigured boot order
  ■ Loose cables
  ■ Corrupt hard drive or corrupt hard drive sectors
  ■ Viruses or malware

Fixes to the Most Common Issues

There is no possible way to make a comprehensive list of fixes, nor an exhaustive one. However, I will try to give some of the most common ways that you could fix the above issues. It is important that if this tutorial is unable to help, that you get further support from the forums of Tom's Hardware or a support professional.

Corrupt boot sector or files, corrupt MBR

This is by far one of the hardest issues to fix, though it is not impossible. You can try the following troubleshooting, though due to hardware differences, it may be different from computer to computer.

The first option here would be to insert your Windows OS disc or your Windows Recovery disc. When prompted, run startup repair and let Windows automatically restore your PC. Windows should automatically replace the bad files to let you boot. In more extreme cases, you may have to do manual boot repair. If you boot into the OS you can access the command prompt where you can run the following commands to try manual repair.




Misconfigured boot order

This issue is quite a bit easier to fix. A misconfigured boot order can be caused by a variety of things, and this means that instead of booting from your HDD, your PC is trying to boot from another disk, perhaps a flash drive or DVD drive. To fix this, you will need to enter your system BIOS settings. When you start, you will be prompted to press a key to setup the boot order. It will look like this (notice the red circle, here you'd press F11):



Most older computers will be using legacy BIOS, so their boot menu will look like this:



Newer systems will be using UEFI, which looks like this:



In legacy BIOS, you will use the keyboard to switch the order. You will want to switch your HDD to the first spot. In EFI, you can simply click the boot order to switch it.

Loose cables

This issue is pretty self explanatory. Simply open your case and check that your HDD (SATA) cables are plugged in completely to both the HDD and the motherboard.

Corrupt hard drive or HDD sectors

In this scenario, the HDD itself is at fault. HDDs use spinning discs which can be prone to malfunctions. A corrupt HDD can usually be fixed by reformatting, but sometimes corruption can be a sign of worse things to come. It would be wise to replace the HDD at this point, as it may soon die.

You can use the command prompt as shown above, and run chkdsk. Chkdsk will scan for errors and bad sectors. It will fix them automatically, if possible.

Viruses or malware

It's inevitable to occasionally get infected. Some malware is much worse than others however. Malware can be as simple as showing you more ads on websites, to as bad as completely wiping your HDD (yes these unfortunately do exist, see: http://arstechnica.com/security/2013/06/hard-drive-wiping-malware-part-of-new-wave-of-threats-targeting-south-korea/). Malware could play a role in killing your boot sector, and AVG's Linux-based rescue disk is a great software to try. You will need access to another computer with DVD burning capabilities or a flash drive.

AVG's rescue software can be found here: www.avg.com/us-en/avg-rescue-cd

You will need to burn this to a DVD or flash disk and boot from it. Once you are booted, you will see a screen similar to this:



Follow the instructions to automatically scan and (hopefully) repair your system.

Wrapping Up

This tutorial was designed to try to fix the most common boot problems that occur on Windows-based systems. Of course, to design an exhaustive tutorial would be impossible. Hopefully you can fix your problems following this guide, and for further support, you can use the forums here at Tom's Hardware or you could contact your local computer support personnel.