> Setup was unable to use the existing partition

Quickly Fix "Setup Was Unable to Use the Existing Partition" Error

Overview of "Setup Was Unable to Use the Existing Partition" Error

In most situations, we could install Windows smoothly since setup gives detailed instructions in each step, but there are many unexpected things happening. For example, in the Where do you want to install Windows interface, you may receive the following error message:

"Setup was unable to use the existing partition because the system volume does not contain the required free space"

Why does the error appear and how to fix it? See the following part to get answers.

Why Setup Was Unable to Use the Existing Partition? Here Is The Answer

To better explain this issue, let's see an example at first.

I'm going to dual boot Windows 7 and Windows 8 with Windows 7 pre-installed. However, when I choose to install Windows 8 to a 150GB partition, I receive the error message "Setup was unable to use the existing partition because the system volume does not contain the required free space". Clearly I have enough free space… It shows 149.9GB free space left. I also formatted and deleted that partition and I tried again with 201gb, and no luck. : ( What should I do? Below is the screenshot in Where do you want to install Windows.

setup was unable to use existing partition

You might also have the same doubt why a 150GB partition with 149.9GB free space doesn't contain the required free space to install Windows 8, right?

Actually, users should focus on the keyword System Volume in the error message. Among all 4 partitions shown in the screenshot above, the one which is labeled as System Reserved is the system volume, but NOT the 150GB logical one where we are going to install Windows. We can clearly see this 100MB system partition only has 0 free space left so that it does not contain the required free space to save Windows 8 boot files. Therefore, Setup was unable to use the existing system partition to install Windows 8.


1. No matter which version of Windows you are running, Windows 7, Windows 8/8.1, Windows 10, Windows Server 2008, or Windows Server 2012, as long as the system partition does not have enough space to hold boot files of new Windows, you'll receive the very error message.
2. Under Legacy BIOS boot mode, the system partition is called system reserved partition, while in UEFI boot mode, it is called EFI system partition.

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Well, how can we fix this issue? Below is a step-by-step tutorial.

Follow Our Tutorial to Fix "Setup Was Unable to Use the Existing Partition" Error in Few Steps

In the tutorial, considering different purposes, we give different solutions.

To Install or Reinstall Windows to Overwrite Old System

If you plan to install or reinstall new Windows to overwrite your old system, there are 2 choices for you. One is to delete or format the system partition, and the other is to delete all contents saved in system partition.

Option One: Delete or Format System Partition
If your Windows is still bootable, please download and install MiniTool Partition Wizard, which is a free partitioning tool running on Windows platforms, to your computer.

Then, start and launch the program to get its main interface:

delete system volume using partition wizard

Here, users just need to select the system reserved partition or EFI system partition, click "Delete Partition" or "Format Partition" feature from the left side, and finally click "Apply" button to make the change finally performed.

However, if Windows can't start, you need to use MiniTool Partition Wizard Bootable Edition. It is embedded in the Professional Edition or more advanced editions. If you are not a Server user, you can buy the Professional Edition to get Bootable Edition.

Here are two tutorials which tell you how to get and use Bootable Edition:
1. How to Build Boot CD/DVD Discs and Boot Flash Drive with Bootable Media Builder?
2. How to Boot from Burned MiniTool Bootable CD/DVD Discs or USB Flash Drive?

After you enter its main interface, you can delete or format the system partition with it.

Tip: if you choose to delete system partition, there might be no system partition after successful installation, while formatting partition could keep the system partition.

In addition, if you just want to delete system partition, you can add the unallocated space released by system partition to other partitions like partition C using the function "Extend Partition" of Partition Wizard. As to how to enlarge a partition, you'll find specific steps in the section How to Extend System Partition without Data Loss.

Once the system partition is deleted or formatted, the error message "Setup was unable to use the existing partition because system volume does not contain required free space" shouldn't appear there.

Option Two: Clear Contents Saved in System Partition

Tip: this method is recommended only when your Windows is still bootable.

Please start Windows and open the system volume, then go to Folder Options (under different versions of Windows, name for Folder Options might be different), check "Show hidden files, folders, and drives", uncheck "Hide protected operating system files", and click Apply button.

unhide system partition

After that, files saved in system partition should be visible. At this time, users only need to select all those files and delete them.

Once system partition is emptied, it should have enough free space to reinstall Windows.

"Deleting, formatting, or clearing system partition could fix the error "Setup was unable to use the existing partition" if you just plan to replace old Windows. Recommend this method to your friends."

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But what if we plan to dual boot system rather than reinstall? Keep reading the post to get the corresponding solution.

To Dual Boot Windows

If you want to install another Windows with keeping the current one, to delete system partition is not recommended, because it will make the existing system unbootable since the partition saves boot files for existing systems.

But even if you mistakenly deleted the system partition, we still have a fix. View the recommended post to get solutions.

Top Recommendation

Delete System Partition Windows Can't Boot – Fixed It Now
Windows can't boot after you mistakenly delete system partition? Now you can make your Windows bootable again in 2 simple ways.

And the best solution for users who are configuring dual boot is to enlarge the system partition, which brings no harm for Windows to boot and function.

How to Extend System Partition without Data Loss

To perform this operation, you need the help of third party partitioning tool since Windows Disk Management does not allow users to do it.

Here, MiniTool Partition Wizard Bootable Edition makes extending partition nothing more than a child’s game.

Just as it is mentioned above, you should buy a paid version, build Boot CD/DVD Discs and Boot Flash Drive, and then boot your computer from it to solve your problem.

Tip: if you are running Windows in Legacy BIOS + MBR mode, please set USB flash drive or CD/DVD as the first boot device in BIOS.

After successfully booting from Partition Wizard Bootable Edition, we will see the window below:

extend system partition select the system partition

Here, all disks and partitions are shown. To extend system partition, please select this partition and choose "Extend Partition" feature from the left action pane.

extend system partition choose a partition to take free space

Then, from the drop-down list of "Take Free Space from" please choose an existing partition or unallocated space, and drag the sliding handle to decide how much free space to take to extend system partition. After that, click "OK" to go back to the main interface of the program.

Tip: you can take 100MB or more free space to extend system partition, depending on your own demands.

extend system partition apply changes

Now we can see system partition has been enlarged, but this is just a preview effect. Please click "Apply" button to make all changes finally performed if the preview effect is desired.

Trick: if you are running Windows under UEFI/GPT mode, most probably there is a 128MB or 16MB (for Windows 10) Microsoft Reserved partition (MSR) between the EFI system partition and the partition where you want to take free space. Under this situation, please delete the MSR partition in Partition Wizard, and then perform operations mentioned above to enlarge system partition. Deleting MRS partition does not bring any damage to Windows.

After successful extending, you should be able to continue to install Windows.

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To Dual Boot Mac OS X and Windows

It's relatively difficult to fix the "Setup was unable to use the existing partition" error if the error emerges when you are installing Windows to Bootcamp partition on Mac.


Before doing any operation, please backup your Mac OS as well as other important data, because one of our methods requires deleting Mac OS partition.

You can search on the internet to see whether there is partitioning tool for Mac to enlarge the system partition without data loss. Disappointingly, so far we haven't found such a program. If you discover one, please share it in the Comment part so as to help more people. Much appreciate!

However, if you don't want to use third party partitioning program, you'll need to delete both EFI partition and Mac OS partition, then reinstall Mac system without creating the EFI system partition or creating a larger EFI partition, and next install Windows to Bootcamp partition.

Therefore, if you are planning to dual boot Windows and Mac, once again please backup Mac OS X and other important files.

Now, our methods for the error have been shown. Just try the correct one by considering your practical situations, reinstall Windows, dual boot Windows, or dual boot Mac OS X and Windows. Should you have any problem on this error, please leave us message in Comment part.

Further Reading: Why System Volume Does Not Contain Required Free Space

Since Windows 7, system partition and boot partition could be separate. Therefore, installing more recent Windows OS on a non-partitioning hard disk will create an additional partition, which could be System Reserved Partition (on MBR disk) or EFI system partition (on GPT disk). And its size could be 100MB, 260MB, 350MB, etc., depending on versions of Windows as well as hard disk formats.

Well, what is EFI system partition and system reserved partition? Below is a brief introduction.

EFI System Partition (ESP)
The ESP is a FAT32 formatted partition containing the bootloaders or kernel images for all installed operating systems, device driver files for hardware devices present in a computer and used by the firmware at boot time, system utility programs that are intended to be run before an operating system is booted, and data files such as error logs.

System Reserved Partition (SRP)
The SRP contains the Boot Manager and Boot Configuration Data for all installed operating systems. It is always located before partition C and marked active. When your computer boots, the Windows Boot Manager starts up and reads the boot data from the Boot Configuration Data (BCD) Store. Your computer boots the boot loader off the System Reserved partition, and it boots Windows from your system drive.

That is to say, this partition stores boot files rather than Windows system files, and boot files for all installed Windows will be saved to this partition by default if there is such a partition. And the more versions of Windows installed, the more boot files saved. The following 3 examples may help you better understand this issue.

Example 1

We previously installed Windows 8 with creating the system reserved partition and partition C, and then plan to install Windows 10 to C to replace Windows 8. For this case, Windows 10 setup will format partition C to clear all its files, but boot files for Windows 8 are still kept complete in system reserved partition. Under this situation, if we install Windows 10, the system partition should hold boot files of Windows 10. As a result, it is very likely to run out of space, and then we might receive the error message "Setup was unable to use the existing partition".

Example 2

We previously installed Windows 8 to create a system partition, and now plan to install Windows 10 for dual boot. Under this situation, if the system partition does not have enough free space to contain boot files of Windows 10, we will receive the very error message.

Example 3

We previously installed Mac OS X on a Mac machine with creating a EFI system partition, and then plan to run Windows on this machine. Since boot files for Windows will also be saved to the EFI partition, it is very likely to run out of space.

Now you should know why Windows system volume does not contain required free space when installing or reinstalling Windows.

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