What is the System Reserved or EFI Partition in Windows?

If you have ever installed Windows by yourself, you may have run into the situation where Windows setup tells you it’s going to create a System Reserved partition or EFI System Partition for system files. The size of this partition is 100 MB. The exact prompt is

You only get this dialog and this additional system reserved partition in certain scenarios. Normally, if you click OK at the prompt, your partitions will look like this:

The System Reserved partition is created when you are using a disk that is using legacy BIOS and the MBR (Master Boot Record) partitioning scheme. The System Reserved partition is 100MB in size, but only has data worth 30 MB.

If you are using a computer with UEFI BIOS and GPT (GUID Partition Table) partitioning scheme, then it will create an EFI System Partition. The size is exactly the same, though.

So what exactly is on this special partition, do you really need it and how can it be removed? Let me go ahead and answer those three questions separately.

What is the System Reserved/ EFI (100MB) Partition?

If you go in and actually view what is stored in this partition, you’ll see something like this:

Basically, the folder contains the following files and folders:

So what is all this for exactly? The partition has two main functions. First, it stores the Boot Manager code and the Boot Configuration Database. The second thing it does is store the startup files needed by BitLocker Drive Encryption. If you end up using BitLocker to encrypt your entire hard drive, you don’t have to re-partition your system to enable it. If you don’t plan on ever using BitLocker, then that means you’ll never need this special partition.

Do you Need the System Reserved Partition?

The short answer is that if you already have it, then YES you need it. You cannot delete it because it contains boot files necessary to load Windows. Unfortunately, once it has been created, there is no way to get rid of it. If you want to have a system without the extra partition, you can only do it during the Windows install process.

How to Remove System Reserved Partition?

Like I mentioned before, you can’t remove it on an existing installation of Windows. However, you can choose not to create it when you are installing Windows on a new system. There are a couple of ways to do this.

1. Use Existing Partitions – Windows will only create the system reserved partition if you create a new partition on a disk that has no partitions created. It will also create it if you delete all the current partitions on the disk and then create a new one. If you want to avoid the extra partition, just use whatever partitions are already on the system. To do a clean install, you can just format an existing partition instead of deleting all partitions.

2. Partition Before Installing – The second way to do it is to use a third-party tool or a different Windows installation disk (like Windows 10 or Windows 7) and partition the disk before you start the Windows setup. If you only have the Windows install media with you, there is a way to do it, but it require a little more work.

Basically, when you get to the first screen in the Windows setup, press SHIFT + F10, which will open a command prompt window. This works on Windows 7, 8 and 10 installations. Then type the following commands, pressing Enter after each line.

Then just continue with the Windows installation and choose the partition that you create with the above commands. Since it’s an existing partition, Windows will not create the system reserved or EFI partition.

3. Trick Windows Setup – The last way to do it is a little trick in Windows setup. Basically, delete all partitions and then create a new one while in setup. It’ll tell you it’s going to create additional partitions and you click OK. Now you’ll have what I have shown in the second screenshot in this post above.

At this point, you simply delete the primary partition, which will give you a prompt saying something like “This partition has system files and if you delete this partition, all data will be lost“. Click OK and then you’ll be left with just the system reserved partition and unallocated space.

Now click on the System Reserved partition and click on Extend. This will make the System Reserved partition the size of the entire disk instead of just 100 MB. Finally, you have to click on Format to convert the System Reserved partition into a normal partition.

Hopefully, that clears up a little bit about what the system reserved partition or EFI system partition is for and how you can manage it. Enjoy!