What Is A System Reserved Partition?

Many of us have likely seen the 100MB “System Reserved” partition found on every Windows 7 installation. It can be found, by default, along with all your other hard drive partitions at the beginning of your disk. Many are left wondering what purpose this partition serves and why it’s there in the first place.

When you choose unallocated space to install a fresh new Windows operating system or Windows Server, a System Reserved Partition is generated. This partition includes the Boot Manager Code, the Boot Configuration Database, and the startup files needed for BitLocker Drive Encryption.

Can “System Reserved” Partition Be Changed Or Removed?

As you may imagine, this has led some less experienced users to wonder if Windows deletes or modifies this partition when doing a major upgrade such as a Service Pack or significant version upgrade from 7 to 8 to 8.1, etc… I’ve seen many people ask how to delete the system reserved partition to free up some unallocated space. 

I’ve also seen many posts claiming that the System Reserved partition is essential to your Windows installation and can’t be removed or modified in any way. Well, both of these points are somewhat incorrect. The “System Reserved” partition can indeed be altered/changed/removed, and in this article, we’ll find out how…

If you open a command prompt with administrator privileges (navigate to Start > All Programs > Accessories > Right-click on Command Prompt and select Run as Administrator), you will get a different result when typing the dir command depending on what edition of Windows 7 you have installed.

If you have Windows 7 Professional, Windows 7 Ultimate, or Windows 7 Enterprise installed on your machine, the dir command from a CMD prompt will show you two partitions of interest. If you have any edition of Windows 7 Starter, Home Basic or Home Premium installed on your machine, then the System Reserved partition is NOT visible when looking at the list of Disk(s) via a Command Prompt… Confused yet? 

This seems to cause all kinds of issues for people wondering what’s going on and why this partition doesn’t seem to show up when they expected it to be there in certain circumstances. Microsoft has given us an almost useless page about these confusing partitions to further add to the confusion.

There are also two different versions of this “System Reserved” partition, both labeled as “System Reserved,” but one is 100MB, and the other is 300MB. The larger partition is used with EFI hardware (UEFI), and the smaller one is used on Legacy BIOS machines. Most new computers will use UEFI rather than legacy BIOS, so Microsoft typically uses the 100MB version to avoid confusion, but loads of people still use older PCs with Legacy BIOS, so they stick with using the larger 300MB version by default… 

How We Change Or Remove The System Reserved Partition:

We do this by using a built-in disk management utility in Windows that allows you to dynamically change or remove these partitions and many other types of partition and storage-related tasks. The disk management utility can be accessed from the Computer Management application, made available via Start > Control Panel > Administrative Tools on most machines. It can be found under System and Security > Administrative Tools.

When opening the Disk Manager, you will see a graphical representation of your system’s hard drive(s) at the top with any storage devices such as CD/DVD drives, USB sticks, etc.… shown below that. Unallocated space on your hard drive is displayed in black, while partitions are offered in a different color depending on their type. Simply right-click on the partition you wish to change or modify and select appropriate options from the context menu to manage partitions. The choice we are interested in is Delete Volume.

When you click this option, an additional confirmation prompt will be displayed asking if you want to delete the selected volume (partition). Here you can choose to remove all data on that partition by selecting Yes, but keep the drive letter assigned or Remove files and clean the drive (recommended), which gives you a final prompt afterward where you can type Y or N as appropriate.

Important Things To Note

1: Changing/removing/modifying the System Reserved (100MB) and other partitions like this will cause Windows 7 (and previous versions of Windows, including XP, etc., etc.) not to boot unless we reverse these changes. The boot loader code in Winload needs to locate and use these reserved system partitions for Windows to boot correctly.

2: When we make changes like this, the data on the ~~System Reserved partition (100MB) will become corrupt or lost if we don’t reverse these changes when we’re finished.

3: If we want to replace the contents of the 100MB System Reserved partition, we need to recreate all of its content and structure in its new location.


That said, we can easily modify the size and position of this System Reserved (100MB) partition or delete it entirely with another third-party tool such as Parted Magic Disk Editor, but when we’re finished, Windows will not boot to anything other than a startup repair screen because the system reserved partition is no longer there for Winload to use when loading Windows. This means that to get Windows back up and running again, you would have to resort to using a Recovery Console-like install disk, CD, or DVD to access chkdsk, which can fix file corruption, etc

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