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

15 Oct 2010   #31
Night Hawk

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

The repair tools are not on the 100mb partition there. That holds the BCD store. When looking at the root of C with all protected system files and folders visible you won't find the "boot" folder if the 100mb was created by the 7 installer.

Now when going to install 7 on a preparitioned drive the 100mb will be omitted where you will then notice the boot folder on C as it had been all along with Vista. For the typical install with the 100mb present having allowed the 7 installer to partition the drive(1st image) the initial view to get a look at what was actually on it was seen with a live cd(2nd image).

Having restored an image of the main drive to a second identical drive the 100mb was assigned a drive letter where you could have a more extensive look in the folders present. Note the recycle bin and system volume information were added once a drive letter was assigned and the small partition was initialized.

As far the F8 options to use the startup repair tool or the "Last configuration known to work" options seen following a hard boot the only time they are available is after Windows was shutdown improperly where the two are presented automatically due to the crash of something. They are not regular F8 options by default.

Attached Thumbnails
What's on that 100MB partition? Can I delete it?-system-reserved-3-100mb-partition-viewed.jpg  
Attached Images
What's on that 100MB partition? Can I delete it?-system-reserved-1-100mb-shown-dm.jpg What's on that 100MB partition? Can I delete it?-system-reserved-2-100mb-viewed-other-os.jpg 
My System SpecsSystem Spec
15 Oct 2010   #32
Bare Foot Kid
Microsoft MVP

W 7 64-bit Ultimate

Quote   Quote: Originally Posted by hacker555 View Post
I was just wondering, cause there is a lot of confusing info in this topic, if I could delete this partition and perform a low-level format on my disks using a couple of programs of hirens boot cd.
My win 7 broke down recently and I just formatted the second disk and put XP on it, cause I don't have time to deal with win7 problems right now... So I want to keep XP for now and reinstall it after the low level format of the disks... So my question is...can I mess with the partition if I plan on reinstalling the OS?

Thanks for any response. =)

Hello hacker555, welcome to Seven Forume!

Have a look at these tutorials at the links below for some ideas.

Partition Wizard : Use the Bootable CD

Dual Boot : Create Partitions Using PWBD
My System SpecsSystem Spec
15 Oct 2010   #33
Microsoft MVP


I just checked (again) and WinRE is placed on the F8 Advanced Boot Options menu at all times by the 100mb SysReserved partition.
My System SpecsSystem Spec

15 Oct 2010   #34

Windows 7x64 Home Premium SP1

If you have a 100MB partition (or others) that you want to poke around in but maybe are a bit afraid of accidentally harming your current system, then just make an image with Macrium Reflect and mount it by double clicking. Right click the mounted drive (Computer view) to dismount. Just select the 100MB partition to image (take < a second). You can't use Windows imaging for this.
The screen shots show what's in mine.
MS do talk about the ability for the OS to place some recovery and security tools here but I don't see them. Second screen shot is the contents Boot folder. Others may my find some tools in there.

Attached Images
What's on that 100MB partition? Can I delete it?-sysres.jpg What's on that 100MB partition? Can I delete it?-sysresboot.jpg 
My System SpecsSystem Spec
15 Oct 2010   #35
Microsoft MVP


So where does WinRE come from? I've never seen it in F8 Advanced boot tools menu except in some factory OEM unless one has the SysReserved partition.
My System SpecsSystem Spec
15 Oct 2010   #36

MS Windows 7 Ultimate SP1 64-bit

That WinRe (Windows Recovery Environment) which is really a modified Win PE (Pre-execution Environment). Now at one time I knew the answer to your question. Alas, old-timer's has set in and also I deleted it from my computer. What I may do, since I also want to test a couple of other things, sacrifice my present OS on my Asus netbook and get a couple of answers.

What I know for 100% is that as long as you have a System Repair Disc, then you don't need any recovery stuff an your computer.

the answer will not be tomorrow but let's say within the next three weeks.
My System SpecsSystem Spec
16 Oct 2010   #37
Night Hawk

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

If you look back at two of the three images I posted earlier you will notice I used two different methods to go through the 100mb folder present to explore them. The first was while booted from a live ubuntu cd until restoring the second drive with an image of the host where the 100mb copy could be mounted and given a drive letter for viewing.

Besides the Recycle bin and System Volume Information folders you typically see on any drive the boot folder was the main concern not being present at the root of C as a system protected folder there. That's where you look to find the BCD store. When a drive is prepartitioned and formatted the boot folder is then seen on C not having the separate partiton created for it.

With select Linux distros a small dos area when seeing a particular drive made bootable is reserved for the failsafe even when the mount point "/" is directed at the root or some other partition. Apparently MS decided a separate boot partition would be isolated from things like rootkits as well as easier to see startup problems repaired since this acts like an archive of the boot information and hidden from normal view by default preventing any accidental deletion.

Ever use CCleaner and just to wonder why this odd seemingly not used folder is sitting on C and you want removed? Gee it says boot but the bootmgr file is found at the root of C not there. Should I delete this odd looking folder? and then wonder Windows won't start?

Due to the actual small amount of actual drive space used it does seem a bit odd that MS used that large of boot partition when the mbr is seen in the first few kilabytes of the drive?! A 100mb or just under 10 3 1/2" floppy disks worth of space that is.

OEM recovery partitions on the other hand run 5-14gb depending on version and how much bloatware a particular model sees. MS likely figured who was going to miss 100mb? off a 250gb or larger drive to begin with? especially when a novice user for example is not even aware of it.
My System SpecsSystem Spec
16 Oct 2010   #38
Microsoft MVP


It apparently is larger than needed because System Volume file expands when imaging. We have had a couple of cases where image including 100mb failed because files had been written there and SysReserve needs approx 34mb for SysVol to expand in order to make an image.
My System SpecsSystem Spec
16 Oct 2010   #39

Windows 7x64 Home Premium SP1

A quote from MS technical data
"System Partition Requirements

Basic system partition requirements are:
  • Must have at least 100 megabytes (MB) of hard drive space.

  • Must have enough free space to create shadow copies of the partition.

    • If the partition is less than 500 MB, it must have at least 50 MB of free space.

    • If the partition is 500 MB or larger, it must have at least 320 MB of free space.

    • If the partition is larger than 1 gigabyte (GB), we recommend that it should have at least 1 GB free.

    Note We recommend that no other files are placed on the system volume, and we recommend that you discourage end-users from storing files on this partition, to avoid filling up this space.
  • Must be configured as the active partition.

  • Must not be an encrypted partition.

  • Must be formatted as NTFS for BIOS-based systems."
It has also been stated that MS introduced this system reserved partition ahead of standard practice for Windows on UEFI firmware machines.
screen shot is from MS.
To me it seems sensible to separate out this booting function for multibooting.

In another thread (Ted) BareFootKid pointed out that initially MS wanted this partition to be 200 MB.

Attached Thumbnails
What's on that 100MB partition? Can I delete it?-uefi1.jpg  
My System SpecsSystem Spec
16 Oct 2010   #40
Night Hawk

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

MS intentionally likes to leave more space then actually needed for various things. If you note the 1-8mb amount of unallocated drive space when partitioning with the MS drive tools on XP, Vista, or 7 that's being reserved for changing a basic volume(default for desktops) into a Dynamic volume(servers mainly) while only 1mb was ever required.

You won't miss the 6-7mb used while it still is over what is need for the conversion. The recycle bin wouldn't even be on the 100mb unless assigning a logical drive letter to it since typically you would simply fill it up too fast. Omit that from the formula there.

Apparently the problems seen with that are particular to a 3rd party program being used which was?

Every image tested by restoration since the new build was up so far has been a success and includes the 100mb. But this is with the option in the Control Panel>Backup & Restore being used. Previously Macrium's Reflect had been tried out and actually failed when considering the image made at the time as invalid due to the date having a fresh copy of Windows on as well as the reinstallation of Reflect wouldn't accept the previous install's image.

Acronis works well for restoration to secondary drives and allows you to mount an image like seeing a second C drive appear for adding and removing files from an existing image. After the latest dual boot of images that was found to restore with the 100mb partition while to the second drive.

(Fortunately I had also gone with the full retail version after trying the WD freebie since that worked the best.)

The image here however will likely be made with the 100mb removed entirely from the host/boot since the partitioning had been done by the W7 drive tool during the installation this last time around. Previously the drive was already to go with a brand new primary and no 100mb seen using GParted live.

In fact it was a first for the new build last spring to even be seeing it on here since the drives used for the 7 betas and RCs had already been in use for the former dual boot at first.
My System SpecsSystem Spec

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

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