By AOMEI / Last Updated January 16, 2020

Why create partition before installing Windows 10/8/7?

By default, Windows will generate a system reserved partition (on MBR disk) or recovery partition (on GPT disk) and C: drive if you select an unallocated space to install Windows operating system (OS). Since GPT disks can have multiple primary partitions as you like, it is no big deal to have one or more extra small partitions on a GPT disk, but things will be different for MBR disks, because you can have at most 4 primary partitions on a MBR disk.

If your computer supports UEFI boot mode, you can convert MBR to GPT disk without data loss. Otherwise, for those people who want to install multiple OS on one MBR drive, the 4 primary partitions are really precious. Besides, you can only have three primary partitions if you have logical partition(s) on the same disk. Therefore, to make full use of the primary partitions is to allow Windows to be installed into one partition without generating a system reserved partition or system recovery partition. The only way to prevent Windows from creating another partition is to partition hard drive before installing.

Partition a hard drive during Windows setup

Windows build-in tool, Disk Management or Diskpart.exe can be used for hard drive partitioning. Disk Management can only be used when OS has been successfully loaded, so you can use Disk Management to create a new partition for another OS if you already have windows installed. If you want to create partition without Windows pre-installed on the hard drive, you can use a Windows installation disc to run Diskpart. The specific steps listed below:

1. Insert the installation disc, and boot your computer from it.

2. At the Windows Setup screen, press Shift+F10 simultaneously to open a command line prompt. If you use the New button to create partitions, it will generate a system partition for an MBR disk.

Where to Install

3. Type “diskpart” and press Enter.


4. At Diskpart>, run a few lines of commands to create a new partition:

◆ List disk
◆ Select disk [disk number]
◆ Create partition primary [size=n]

For example, the following command is to create a 30000 MB primary partition on disk 0:

◆ List disk
◆ Select disk 0
◆ Create primary partition size=30000

Create Primary Partition

5. Then you will have created a partition around 30GB. You can use this command to create more partitions or exit.

If your hard drive has enough space, then it is recommended to allocate more than 100GB to the system drive because Windows update, installed programs, and other system files will keep consuming space on system partition. If you don’t have a Windows installation disc, then you can use third-party free partition manager software to create partition without operating system.

Create partitions without OS pre-installed with free partition manager

AOMEI Partition Assistant Standard is a freeware for disk and partition management that provides the ability to create bootable media, so you can partition a hard drive with or without OS pre-installed. If you have Windows installed on your hard drive, you can just free download this software and start to partition your hard drive without losing data. Let’s see how it works:

1. Boot your computer from the AOMEI bootable media you created. It will lead you to the main interface of AOMEI Partition Assistant.

2. Right-click on unallocated space or a partition that is big enough to create a new partition, and then choose Create Partition button.

Create Partition

3. At the next screen, drag the slider or enter the amount of space to specify the partition size. You can also click Advanced option to see more options. Click OK when settings are done.

Resize Partition

4. The program allows you to preview the partition layout without making any changes to your hard drive. If no problem, click Apply to run the operations.


It is really a good shot to create partition before installing another OS on your hard drive. Besides NTFS, AOMEI Partition Assistant also supports many other file systems including FAT32, FAT16, FAT12, exFAT, ReFS, and Ext2/Ext3/Ext4. The paid edition, like AOMEI Partition Assistant Professional or AOMEI Partition Assistant Server, provides even more advanced features like enabling you to migrating OS to GPT disk, converting dynamic disk into basic, etc.