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Windows 7: Dual boot (7+7) bcd entrys


21 Apr 2011   #1

Windows 7 Home Premium
 
 
Dual boot (7+7) bcd entrys

I have a question about the long (GUID) looking entries in the bcd file/store/thingy.

I'm setting up for dual boot, Windows 7-Home Premium (x64) on the C: partition and Win7Pro on the D: partition.

I have them both installed and made partition images of both. Everything works fine, I have the bdcedit thing working for a nice dual boot situation.

So now that I have a nice D: image of Win7Pro32, I want to wipe D and install Win7Pro64, will it use the same bcdedit entry? or does that long GUID looking thing point to a specific install.

In other words if I want to occasionally wipe/restore the D partition to test things in x32 then x64, am I going to have to have a 3rd entry in the bcd file/store/thingy in my boot screen?

My System SpecsSystem Spec
.

21 Apr 2011   #2
Microsoft MVP

 

Boot the Pro installer, use Custom>Drive Options to format the target partition, install. Windows 7 will configure the Dual Boot with the other OS.

If not, install EasyBCD 2.02 when it boots up after install, Add the other OS, then clean up any stray boot listings on Edit Boot Menu tab.
My System SpecsSystem Spec
21 Apr 2011   #3

Windows 7 Home Premium
 
 

Quote   Quote: Originally Posted by gregrocker View Post
Boot the Pro installer, use Custom>Drive Options to format the target partition, install. Windows 7 will configure the Dual Boot with the other OS.

If not, install EasyBCD 2.02 when it boots up after install, Add the other OS, then clean up any stray boot listings on Edit Boot Menu tab.
Well thanks for that, but I think your reply was for another post.

I already have two OS's installed and a functional dual boot setup. Please re-read my scenario (3rd sentence onward in the OP) about re-imaging the same (D) drive between x32 and x64.
(leaving C drive alone with an x64 build on it)

Let me re-phrase the question: is the GUID (or UUID) of the bcd store entry specific to an instance of an installation, or just used for a unique entry in the bcd store/table?
My System SpecsSystem Spec
.


21 Apr 2011   #4
Microsoft MVP

 

You said you want to wipe the Pro 32 partition to reinstall Pro 64. I gave you the steps to have the Windows 7 installer autoconfigure the Dual Boot.

If you want to switch back and forth, after reimage you might have to add the reimaged OS using EasyBCD 2.02. Normally overwriting the partition removes the Boot Listing, but not always.

I just reimaged a friend's Windows 7 from his old PC onto a new laptop's second partition via TeamViewer using Acronis with Universal Restore, then added it using EasyBCD - all without a restart - after which it started up to a Dual Boot menu which I then hid. So there is much flexibility and EasyBCD makes Adding or Editing entries easy.
My System SpecsSystem Spec
22 Apr 2011   #5

Microsoft Community Contributor Award Recipient

ME/XP/Vista/Win7
 
 

Follow gregrocker's advice.
My System SpecsSystem Spec
22 Apr 2011   #6

Windows 7 Home Premium
 
 

Ok thanks for that. I guess I better just let this drop, seems to be apples-n-oranges.

In my OP I didn't intend to ask about installing a multi-boot Windows scenario, or modifying the bcd table/store as it may have sounded, these things I know how to do, my question was supposed to be ...specifically... about the entry in the bcd table/store, that GUID or UUID string in each entry, but never mind, it's no big deal if it's unknown here, I can move forward without that knowledge.

Reading this article it would seem it's not specific to an instance, rather just used as an identifier in the boot manager operation:

http://technet.microsoft.com/en-us/library/cc721886(WS.10).aspx

Thank's all.
My System SpecsSystem Spec
22 Apr 2011   #7

Windows 7 Home Premium
 
 

Just one more thing, this is one of the things that prompted my question in the OP.

When I get into the bcd with the editing tool I see only the current stuff, when I look directly at the BCD00000000 reg key I see more installations (and recovery's), or maybe I'm just not reading things right:


Attached Thumbnails
Dual boot (7+7) bcd entrys-bcd_store_different_objects.jpg  
My System SpecsSystem Spec
22 Apr 2011   #8

Windows 7 Home Premium
 
 

Hmmm, still confused, according to this website the GUIDs are unique to an instance of an install:

Multibooters, Vista Dual and Multibooting - Vista's Boot Files, bootmgr and BCD

(snip)...
"In the BCD store the boot Objects are identified by their GUID numbers, but not all GUIDs are the same. Some are called Globally Unique Identifiers and some are Global Universal Identifiers. The 'Unique' GUIDs are generated for each Vista boot and resume Object and will be unique to that Vista install. They appear to be randomly generated and can have any value. I've found that as long as the GUID held in the bootmgr Object matches the one for the Vista Object, I can change them to any 32 digits I want and everything seems to function normally. The 'Universal' GUIDs have a fixed value, which again appears arbitrary, that will be the same on every computer. The BCD contains separate boot Objects for things like the Memory Tester {memdiag} and the Legacy OS Loader {ntldr} and these Objects have 'Universal' GUIDs. Such Objects still contain the signature and offset of the drive and partition where the item is located and bootmgr does use this information to find it, so configuration changes do have an affect.
"
My System SpecsSystem Spec
22 Apr 2011   #9
Microsoft MVP

W 7 64-bit Ultimate
 
 

Quote   Quote: Originally Posted by Redhouse View Post
Hmmm, still confused, according to this website the GUIDs are unique to an instance of an install:

Multibooters, Vista Dual and Multibooting - Vista's Boot Files, bootmgr and BCD

(snip)...
"In the BCD store the boot Objects are identified by their GUID numbers, but not all GUIDs are the same. Some are called Globally Unique Identifiers and some are Global Universal Identifiers. The 'Unique' GUIDs are generated for each Vista boot and resume Object and will be unique to that Vista install. They appear to be randomly generated and can have any value. I've found that as long as the GUID held in the bootmgr Object matches the one for the Vista Object, I can change them to any 32 digits I want and everything seems to function normally. The 'Universal' GUIDs have a fixed value, which again appears arbitrary, that will be the same on every computer. The BCD contains separate boot Objects for things like the Memory Tester {memdiag} and the Legacy OS Loader {ntldr} and these Objects have 'Universal' GUIDs. Such Objects still contain the signature and offset of the drive and partition where the item is located and bootmgr does use this information to find it, so configuration changes do have an affect.
"
Hello mate.

I thought as much but I wasn't sure enough to advise; thanks for the information.
My System SpecsSystem Spec
22 Apr 2011   #10

Windows 7 Home Premium
 
 

I guess it doesn't matter either way.

My box has only 3 partitions and no hidden sys partition, so (I believe) the bcd stuff is located on the C: partition.

  1. I booted to C: and ran bcdedit /export and saved a copy of my BCD file/store/whatever-it-is,
  2. Imaged my D:, booted to Windows 7 on C:, used diskmgmt.msc to format D:.
  3. Installed Win7x64 (from the cool AIO disc I made from another thread here) onto the D: drive.
  4. Rebooted back to the original build (was C, but the new install changed itself to being C) and ran bcdedit /import and got my original boot manager setting back.

The old bcd was now back in place, my original load of Win7HPx64 was back to C: the new load of Win7Px64 was now on D: (where it was actually installed) and it booted up exactly like before (both did). So it doesn't seem to matter if you pull the rug out from under the bcd entry, it just seems to point to whatever is on that entry and let's 'er rip.

Nothing "complained" about the new instance of Windows 7 not matching the boot table entry (booting an x64 instance from the x32 entry GIUD/UUID) so I guess that whole question is irrelevant.

Now I can swap D images at-will between x32 and x63.

Guess I should have done all this before posting this topic/thread 'eh?.

{Edit} only one thing left to clear up, when booting to D build, it says it's C drive, I'll need to figure that bit out.
My System SpecsSystem Spec
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