Windows 7 bcd file structure

Windows Client. Sign in. United States English. Ask a question. Quick access. Search related threads. Remove From My Forums. Asked by:. Archived Forums. Windows 7 Miscellaneous. Use this forum to discuss miscellaneous issues that cannot be covered in any other Windows 7 forum. Sign in to vote. Hi, This may help you if you're is stuck with corrupt BCD and can't boot to windows and repair with Win7 setup disk is not working. After examining this backup file in our Documents folder using HxD , our first reaction was: "Man, this thing appears to be full of all kinds of needless 'gunk'!

So, the 'backup copy' is not really a true copy. And the differences go well beyond simply changing the path name of its location. So why is this file so 'cluttered' compared to the Windows XP boot. Its first 4 bytes are a big clue: " regf ".

DAT file begins with the same 4 bytes. To test this, we used a disk editor to alter the bytes at offsets 0x 1B8 through 0x 1BB in the MBR first sector of the disk drive by simply adding 1 to each byte.

In previous Windows versions, the OS would still boot up this way; even though there was the possibility some program that used the Disk Signature could then have problems. Note: The same error message, with Status: code of 0x ce , will also be displayed if we change those NT Sig. Only if you edit these bytes back to their original values will the PC boot-up again.

It's also possible to see such an error if your PC is somehow directed to start booting from a drive other than the normal boot drive, and the BCD Store on that drive points to the first drive, which will obviously contain a different Disk Sig.

Because new Windows OS installs often make changes to a primary disk drive, even when installed to a secondary drive! Disconnect all but the disk drive you intend to install a new Win OS on, and in the future you will be able to boot-up the new drive all by itself or using a Boot Menu key without it depending upon some primary disk drive you decided to remove, or that has failed. NOTE: The error shown above is a function of the bootmgr program!

We know this, because the same error message will be displayed after altering the NT Disk Signature on a drive that has had its entire C: Volume where the actual Windows OS resides removed! But how does bootmgr know what those hex bytes should be?

For our small test install of a new Windows 7 OS, this shows where those bytes occurred highlighted with a pink background color ; along with all the other data contained in a BCD Store file. LOG2, but the numbered files are often empty. To clarify: Under most previous Windows installs, such as Windows 98, people who performed multi-booting or simply had many different partitions on their PCs often used a program called Partition Magic to shrink or even completely rearrange the layout of partitions on their disk drives.

But attempting to change where the C: Volume begins under Windows 7 results in a similar BLACK screen error as above; including the same exact message: " Info: The boot selection failed because a required device is inaccessible. BCD store is located in the Boot folder on the active partition. The BCD is a database used by Bootmgr.

It contains the functions of boot. This sequence can vary if the computer is resuming from hibernation or if a non-Windows 7 option is selected during the Windows Boot Manager phase. It is not recommended to move these important and critical windows files neither to a different directory on the same partition nor to a different partition altogether.

Moving these files may make Windows or other programs unstable or even Windows may fail to boot to the desktop. I would not recommend you move these files from their original location. Hope this information is helpful. Was this reply helpful? Yes No. Sorry this didn't help. Thanks for your feedback. If it's at all possible to do this, I would like to know, even if it involves having to use a hex editor and modifying the Boot Sector code and the BCD files.

I may or may not choose to attempt it if this is the only way to achieve this, but even if I don't, I just would like to know for having a better understanding of how Windows Boot Manager works. Feel free to write us back if you have any other query or for any further assistance with Windows.

MBR Boot code, tells system to load "bootmgr" file. Bootmgr file, tells system to get settings from the BCD file and get user input. Once user selects input, use config to load the next stage loading the kernel Does anyone have some insight into this, if what I ask is even possible?