Added by Mahmoud Al-Qudsi, last edited by Mahmoud Al-Qudsi on Jun 26, 2007  (view change)

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The Bootloader

If you've ever had a problem booting into Windows, configuring a dual-boot between Windows & Linux, or getting Mac OS' Darwin Bootmenu to show up, you know what a bootloader is. The bootloader is a application of sorts that tells your computer where on the hard drive it can find the various operating systems and how to turn them on. Typically speaking, the bootloader resides in the MBR (a bunch of data at the start of the hard drive) and/or the bootsector (a bunch of data at the start of a partition). The bootloader in the MBR activates the bootloader on the bootsector (a process known as "Chainloading") and from there your Operating System boots up. It's where all the hard-to-solve problems come from, and it's also where EasyBCD does most of its work.

Windows Vista uses the "BCD Bootloader" (Boot Configuration Data) to launch Windows Vista when you turn your PC on. It's a very powerful application that can give you complete customized control over how your Operating System boots and with what options. With Windows Vista, the BCD Bootloader is restricted to loading Windows Vista, Longhorn Server, and Legacy Windows Operating Systems. The first two are loaded directly, the third isn't directly supported and instead is chainloaded from two files on your hard drive: NTLDR and Boot.ini.

The "Bootloader Managment" Screen

EasyBCD makes it easy to change the bootloader that's installed on your MBR via the Bootloader Management screen:

Picking a Bootloader

This section of the EasyBCD Bootloader Management page allows the user to choose which bootloader resides in the MBR. As of EasyBCD 1.5, the two options available are:

  • Windows Vista "BCD" Bootloader
  • Legacy Windows NTLDR Bootloader

Please note: Using this page will overwrite any existing MBR! If you are using a 3rd party MBR like Grub or Darwin, don't worry, EasyBCD can be used instead. However, if you are using any software that customizes the MBR, such as Roxio GoBack or Acronis TrueImage, the post-boot interface for these applications will no longer be available. See [*this page*] for more information getting these programs to work with EasyBCD.

The Windows Vista Bootloader

The Windows Vista bootloader is installed to your first-boot hard drive's MBR the first time you install Windows Vista, and every time thereafter it is updated or rewritten depending on its status. In order to boot into Windows Vista, the Windows Vista Bootloader must be the currently installed MBR script! From the Windows Vista bootloader you may boot Windows Vista, Longhorn Server, and Legacy Versions of Windows by default. With EasyBCD, this feature-set is expanded to include Linux, Mac OS X, and BSD amongst others.

EasyBCD can be used whether or not the Windows Vista bootloader is installed to the MBR, but in order for any of the settings visible in EasyBCD to take place upon reboot, the MBR must contain the Windows Vista bootloader.

The Legacy Windows Bootloader

The Legacy Windows Bootloader, or NTLDR, is used to boot legacy versions of Windows. NTLDR cannot be used to boot into Windows Vista - to do that you must install the new Windows Vista bootloader. Generally speaking, the only time you'd want to install this bootloader to the MBR is if/when you want to completely remove Windows Vista from your system. The Windows Vista bootloader - through EasyBCD - can load any Operating System that NTLDR can boot and then some; making it almost entirely pointless to install NTLDR to your MBR.

Some cases where you might want to install NTLDR to the MBR include installing Windows XP after Windows Vista or attempting to install a Linux distribution that uses the 2.4 kernel.

Writing the MBR

Once you've picked the bootloader you'd like to use, you can proceed and press the "Write MBR" button. However, please pay careful attention to the following!

Writing the MBR is a very delicate process that requires direct access to the hard drive. This feature shouldn't be used through a virtualization layer or under custom filesystem drivers. Writing the MBR will may result in some rather unexpected behavior!

  • Disrupted I/O access to the hard drive.
  • Loss of data in the process of being saved to the hard drive.

None of these are fatal and EasyBCD takes extra precaution to protect your hard drive. Under almost no circumstances will this result in problems, however, you might want to do the following before writing the MBR:

  • Stop any running torrents - They might become corrupted.
  • Finish burning CDs or DVDs - If you don't, the CD will be corrupt and unfixable.
  • Save any open documents - And wait for the save to finish.
  • Disconnect from network shares - Make sure no one is remotely using critcal data from your hard drive.

If you followed these steps you should be OK to hit that button. Once the process is complete, you may go back to whatever you were doing.