Understanding the EMBR
The first sector (or block of data) on your hard disk is called the Master Boot Record (MBR). The MBR contains the partition table that defines the partitions (or areas) on your hard drive and a small program that transfers control to the first sector (boot sector) of one of the partitions.
The partition table can contain up to four primary partition entries that contain information on where the partition begins and ends, a flag to mark the active (or bootable) partition, and the type of file system used in the partition.
The Extended Master Boot Record (EMBR) specification dynamically extends the capabilities of the system. The EMBR contains a block of code, called the EMBR Loader, and three tables — one for partition information, one for boot file information, and one for information on drivers that may need to be loaded on your system. Each of these tables can contain up to 255 entries. The table in the EMBR that contains partition information is called the Master Partition Table (MPT). This table is used in place of the partition table to contain all partition information.
BootIt BM handles the MPT and partition table by letting you create bootable configurations (or boot items) allowing you to choose which partitions from the MPT are to be placed into the partition table.
The EMBR is usually automatically created on drives connected to the computer when BootIt BM is installed or updated (depending on selected options). This includes both internal and external drives (e.g. USB, eSATA).
When BootIt BM is no longer being used with the drive or other partitioning software has been used on the drive, the partitions in the EMBR and the partition table may no longer be in sync. This can cause problems when using programs that look in the EMBR for partition information (e.g. Image for Windows).
In this case, the EMBR must be removed from the drive to allow the correct partitions to be found and used.
Note: More information on BootIt BM and the EMBR can found in the BootIt BM Manual.
Before you begin...
It may be helpful to make note of the positions, sizes, and types of the current partitions on the drive as displayed by the operating system (Windows, Linux, etc.). This information can then be used to verify that the correct partitions exist on the drive after the removal of the EMBR. TeraByte's free Partition Information utility (PARTINFG) can be used to obtain this information and save it to a file for easy reference. When using this program, note that the MBR view will display partitions in the MBR and the MPT view will display partitions in the EMBR.
Warning: In most cases, the EMBR can be removed easily and safely, without causing the existing partitions (those in the partition table) to be lost. However, due to the nature of the changes being made, there is the possibility of data loss. Backing up any important data on the drive before proceeding is recommended.
Multiple methods to remove the EMBR are detailed below. Advanced users may wish to read through the entire article before selecting which method to use.
Using BootIt BM to Manually Remove the EMBR
- This method requires BootIt BM to remove the EMBR. The procedure can be done from the installed version of BootIt BM or from the BootIt BM boot media. If necessary, download it and create the boot media (CD, USB flash drive, floppy).
- If the drive is external, make sure it's connected and powered on before booting into BootIt BM.
- Boot the computer into BootIt BM. A warning message may be displayed. For example,
A new or altered primary partition was found on HDx which may overlap an existing partition! You should use partition work to check for errors.
Click OK to close the message box.
- Enter Maintenance Mode: From the installed version, click the Maintenance button on the Boot Menu. From the boot media version, click the Maintenance button on the Installation & Recovery Boot Menu (shown if BootIt BM is installed) or click Cancel on the Setup window and then Ok to enter Maintenance Mode.
- Click the Partition Work button on the desktop.
- Select the drive that needs the EMBR removed. Note that the drives may be listed in a different order than shown in Windows/Linux.
- The drive's partitions will be displayed and may indicate that there are errors. If errors are detected, * Errors Exist * will be displayed above the top right corner of the partition list box and the partition(s) with the detected error are marked with an E (located to the left of the partition's size). Please note that only one error will be displayed at a time. After fixing an error, the next error will be displayed (if one exists).
- In most cases, the correct partitions are already loaded into the MBR since the drive was not being used or maintained as an EMBR drive. Click the View MBR button to view the currently loaded partitions. You can use this information, along with the information obtained in the Before you begin section above, to help determine the correct partitions to keep and which to delete.
- Delete the incorrect partitions by selecting the partition and then clicking the Delete button. Caution: Do NOT check either the Clear Boot Sector or Wipe Partition options.
- When only the correct partitions remain and there are no errors reported, click the Change Disk Type button and then click the MBR button to convert the drive to the MBR type. Click Yes to confirm the change.
The correct partitions should now be displayed by the operating system, BootIt BM, Image for Windows, Image for Linux, and Image for DOS.
Using a Disk Editor to Manually Remove the EMBR
Advanced users may prefer using a disk editor to edit a few bytes on the drive to remove the EMBR. If you are familiar with using a disk editor, this method is very quick and easy.
- Run the Disk Editor of your choice and bring up a HEX view of Sector 1 of the drive (note that this will be the second sector).
- The first four bytes of Sector 1 will be 45 4D 42 52 ('E', 'M', 'B', 'R').
- Change all four bytes to 0 (zero).
- Save the sector.
Using MBRWORK to Remove the EMBR
MBRWORK is a free utility provided by TeraByte. It allows you to reset the EMBR area of a drive.
Note: This program only works in DOS.
- Run MBRWORK.
- Change the active hard drive to select the correct drive (option 7).
- Reset the EMBR area of the drive (option 3).
- Exit the program.