Why is separate 100 MB system bootmanager partition not always necessary?


Extraordinary Member
As far as I know Win7 introduces a new Bootmanager system.
At old WinXP times the bootmanager was put into the first bootable partition on the first hard disc.
This partition could contain the actual Windows XP itself in addition.

From Win7 times on Bootmanager should be installed in a separate (only 100 MB small) additional primary partition.
When booting the system at first this Bootmanager "meta" partition is called which in turn calls the actual Windows 7 OS partition.

Ok, currently I prepared three partition on my hard disc:
- 40 GB for Win7
- 100 MB for Bootmanager
- 500 GB for data

When I installed now recently 64bit Win 7 Pro everything was put on the first 40 GB partition.
The installation procedure did not ask where to put the Bootmanager.
Where is it?
Is Bootmanager only created/established when a SECOND OS is installed on the hard disc?

Thank you for answers

Joe S

Excellent Member
I don't think the 100mb partition is created if the disk is already partitioned. I had Vista and partitioned the disk so there were 3 partitions system Restore and Data. I wiped vista and installed windows 7 and don't see any 100mb partition.

That is correct if the disc is already partitioned it does not install the 100 MB when I installed W7 on one my internal hard drives that i had done a format on prior to installation no 100 MB partition was created.
After I got W7 installed I installed Vista Boot Pro 3 it does work on W7 I then went to manage OS entries Tab in Vista Boot Pro and added the drive I had Vista on my machine is now a dual boot machine with W 7 as my default OS.
There are other boot loaders out there just Google for them.
Here is one a lot of people use and recommend Download EasyBCD 2.0.2 - NeoSmart Technologies


Excellent Member
Microsoft Community Contributor
Win 7 will install the small boot partition for some reasons not completely clear, but it puts the boot files in an unlettered partition and makes it a little harder to mess with them. I have also heard it is related the bitlocker utlity. It may also be related to the Repair system, but it seems I can get the F8 key to work without it, but not certain right now.

As has been stated, you can keep it from installing the small partition if the drive is pre-formatted, or if you format it during the install prior to clicking the install button.

The boot files go in the first active partition on the primary hard drive. If there is not an active partition on the primary drive, it will create one. During a normal install, you do not have to create a separate 100mb partition, the install will carve it out of the space you give it.

It may be important that the 100 mb partition is one of the 4 primary partitions allowed on a drive. So, if you will need additional partitions, it might be good to install without it.


Microsoft MVP
Staff member
Premium Supporter
Microsoft MVP
When installing to an unformatted hard drive the Windows install creates that partition to enable booting into recovery mode from the hard drive. If you format the drive first, before running the install it will not be created as it is not necessary for normal running. If you have Windows install disks or have created recovery dvd's from your hard drive recovery partition then you wouldn't need the 100mb partition anyway.


Extraordinary Member
Required if you using Bitlocker
To encrypt drives and to verify boot integrity, BitLocker requires at least two partitions. These two partitions make up a split-load configuration. A split-load configuration separates the main operating system partition from the active system partition from which the computer starts.
I think it is also needed if you have OEM recovery partitions. TypeID = 0x27

During install and not using Bitlocker I create partition which makes small one, then delete large and extend the 100 to end.

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