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Windows 7: What's on that 100MB partition? Can I delete it?

18 Oct 2010   #61
Night Hawk

W7 Ultimate x64/W10 Pro x64 dual boot main build-remote pc W10 Pro x64 Insider Preview/W7 Pro x64
 
 

On a Windows machine the mbr is another MS Dos type partition seen there. That's not one you can view however by mounting it and assigning a drive letter however.

The 100mb is considerably larger and can see the system volume informatio and even recycle bin added when a drive letter is assigned. Disregarding the NST folder for EasyBCD placed there by the latest 2.0.2 version I grabbed another image for an expanded look at it.




Attached Thumbnails
What's on that 100MB partition? Can I delete it?-system-reserved-4-100mb-extended-view.jpg  
My System SpecsSystem Spec
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18 Oct 2010   #62
mjf

Windows 7x64 Home Premium SP1
 
 

Quote   Quote: Originally Posted by Night Hawk View Post
On a Windows machine the mbr is another MS Dos type partition seen there. That's not one you can view however by mounting it and assigning a drive letter however.

The 100mb is considerably larger and can see the system volume informatio and even recycle bin added when a drive letter is assigned. Disregarding the NST folder for EasyBCD placed there by the latest 2.0.2 version I grabbed another image for an expanded look at it.
I'm not sure what I'm supposed to be looking at.
MS make reference to an MSR (Microsoft System Reserved) partition in the context of UEFI but it's not the Master Boot Record.
My System SpecsSystem Spec
18 Oct 2010   #63
Night Hawk

W7 Ultimate x64/W10 Pro x64 dual boot main build-remote pc W10 Pro x64 Insider Preview/W7 Pro x64
 
 

Quote   Quote: Originally Posted by mjf View Post
Quote   Quote: Originally Posted by Night Hawk View Post
On a Windows machine the mbr is another MS Dos type partition seen there. That's not one you can view however by mounting it and assigning a drive letter however.

The 100mb is considerably larger and can see the system volume informatio and even recycle bin added when a drive letter is assigned. Disregarding the NST folder for EasyBCD placed there by the latest 2.0.2 version I grabbed another image for an expanded look at it.
I'm not sure what I'm supposed to be looking at.
MS make reference to an MSR (Microsoft System Reserved) partition in the context of UEFI but it's not the Master Boot Record.
You can't look at the Master Boot Record like you can when mounting the 100mb as a logical drive and seeing a drive letter selected for it or viewing it while booted live from another OS as shown earlier in the thread. The image here is another capture with a futher look having an extra WE window open.

What you are looking at there disregarding the recycle bin and NST folders before making the 100mb available to view is the actual BCD store or 7's boot loader files including the bootmgr and boot.bak files you would otherwise find at the root of the host/boot drive.

Perhaps the best advise for anyone considering removing the 100mb partition itself is to either see that done immediately following a clean install of 7. Reasons?

When you only have the basics not even device drivers on or partitioning the drive ahead of time to avoid a possible disaster of waiting too long and trying to move the 7 primary the 101mb or more needed to the front of the drive. That can take forever and ever and ever.... hours actually depending on large and how much is on it?

The primary itself can become totally unusable with no options for repair and end up being seen as "Raw" and not found when booting live to use the repair tools! Totally lost!

It will not depend on which drive partitioning program is used either. Backing up the backups is the word when ever going to make "any" partition changed especially with a Windows installation that has been in use for some time.
My System SpecsSystem Spec
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18 Oct 2010   #64
mjf

Windows 7x64 Home Premium SP1
 
 

As per my previous screen shot I can see everything on the 100MB system reserved partition, boot manager, BCD store etc and know basically what they do. System Volume information is locked and serves another purpose.
Let's just agree to disagree on what the MBR is.
My System SpecsSystem Spec
18 Oct 2010   #65
mjf

Windows 7x64 Home Premium SP1
 
 
Hopefully the full Picture

I'm confident that what I said earlier is correct except I left out one element of the picture and that is the Partition Boot Record which I believe is the first 16 sectors of the active partition. So the MBR passes control to the PBR which loads the boot manager on it's partition and so on.
So the boot sequence is:

BIOS --> MBR (inc partition table) at start of disk --> [ PBR (at start of active partition) --> Boot Manager (Using BCD) ] --> C:\windows\system32\winload.exe

[....] Key elements of 100MB system reserved for booting

Again here is the Hex of the MBR and the Hex of the first part of the PBR.
To get the PBR Hex I mounted a macrium image of the 100MB system reserved and opened it with a Hex editor.


Attached Thumbnails
What's on that 100MB partition? Can I delete it?-mbr.jpg   What's on that 100MB partition? Can I delete it?-pbr.jpg  
My System SpecsSystem Spec
18 Oct 2010   #66
Night Hawk

W7 Ultimate x64/W10 Pro x64 dual boot main build-remote pc W10 Pro x64 Insider Preview/W7 Pro x64
 
 

All that may amount to nothing some time soon! Researchers one step closer to 'bootless' computer

With a fast snip after just having restored Vista to the second drive you can see the unhidden "boot" folder was always seen on C with the previous version as well as on C when a drive was partitioned and formatted prior to any 7 install. That contains the BCD store while bootmgr and bootsect.bak files are found mixed with the other root files like the hibersys for example.


Attached Images
What's on that 100MB partition? Can I delete it?-vista-7-boot-folder.jpg What's on that 100MB partition? Can I delete it?-vista-drive-viewed.jpg 
My System SpecsSystem Spec
19 Oct 2010   #67
mjf

Windows 7x64 Home Premium SP1
 
 

Quote   Quote: Originally Posted by Night Hawk View Post
All that may amount to nothing some time soon! Researchers one step closer to 'bootless' computer

With a fast snip after just having restored Vista to the second drive you can see the unhidden "boot" folder was always seen on C with the previous version as well as on C when a drive was partitioned and formatted prior to any 7 install. That contains the BCD store while bootmgr and bootsect.bak files are found mixed with the other root files like the hibersys for example.
That research is still in fantasy land. (I worked in research labs most of my life - good press never hurts funding). We are still waiting to see if UEFI will dominate.

My last post describes the way Windows 7 boots now for BIOS based machines.

I'm not sure what point you're making with your last screen shot and comment.
My System SpecsSystem Spec
19 Oct 2010   #68
Night Hawk

W7 Ultimate x64/W10 Pro x64 dual boot main build-remote pc W10 Pro x64 Insider Preview/W7 Pro x64
 
 

Quote   Quote: Originally Posted by mjf View Post
Quote   Quote: Originally Posted by Night Hawk View Post
All that may amount to nothing some time soon! Researchers one step closer to 'bootless' computer

With a fast snip after just having restored Vista to the second drive you can see the unhidden "boot" folder was always seen on C with the previous version as well as on C when a drive was partitioned and formatted prior to any 7 install. That contains the BCD store while bootmgr and bootsect.bak files are found mixed with the other root files like the hibersys for example.
That research is still in fantasy land. (I worked in research labs most of my life - good press never hurts funding). We are still waiting to see if UEFI will dominate.

My last post describes the way Windows 7 boots now for BIOS based machines.

I'm not sure what point you're making with your last screen shot and comment.
If you were following the thread from the start you would since this thread is not about the mbr but the 100mb system reserved partition, what is on it, and if it can be removed. The second screen there shows what you would normally expect to see at the root of a Vista drive as far as the boot folder.

Likewise when 7 is installed on a prepartitioned drive and doesn't see the 100mb boot partition the boot folder as well as the bootmgr and bootsect.bak are instead found at the root of C not on a separate partition. When not found after removing the 100mb those have to be replaced new in order to see 7 run.

It won't matter then what is in the mbr if you don't have the boot files and boot configuration stored locally on C. The boot files have to replaced as well as seeing the new BCD stored created.
My System SpecsSystem Spec
19 Oct 2010   #69
mjf

Windows 7x64 Home Premium SP1
 
 

I have indeed been following the thread and have given an accurate picture of the whole boot process in order to explain what's in, and the role of, the 100MB system reserved partition. In the process it became necessary to explain the role of the MBR and the fact that it does not exist in any partition including the 100MB system reserved and cannot be moved around. To repeat the summary from my earlier post:

BIOS --> MBR (inc partition table) at start of disk --> [ PBR (at start of active partition) --> Boot Manager (Using BCD) ] --> C:\windows\system32\winload.exe

[....] Key elements of 100MB system reserved for booting

This answers the question originally posed at the start of the thread. If the 100MB partition is "System, active" and you just delete it you break that part of the boot sequence shown in bold and your computer will not boot. Can you get rid of it and have your PC still boot? YES - see elsewhere for how.

Addition: The original question posed had a curiosity element to it (which is fine). But it is actually a very fundamental question. I really think it has now been answered.
My System SpecsSystem Spec
19 Oct 2010   #70
gregrocker

 

Anytime you lose System Active drive due to removed Dual Boot, or SysReserved partition being deleted or not reparable via Startup Repair:

Boot the WIn7 DVD or Repair CD, press Shift F10 to open a Command line to mark Win7 partition active using Diskpart: Partition - Mark as Active

Next boot back into the Win7 DVD Repair console or Repair CD, accept any offered repair. If it fails to start after reboot, boot back into Recovery Tools List to run Startup Repair up to 3 separate times with reboots until the MBR is written to Win7 and it starts up. Startup Repair - Run 3 Separate Times
My System SpecsSystem Spec
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 What's on that 100MB partition? Can I delete it?




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