How to install a second Windows on a disk without data loss

In some cases, Windows OS alone may not be enough. For example, you downloaded a relatively old game, and it does not work on modern Windows 10 (and on Windows 8/7 it starts).

By the way, it should also be noted that in Windows 10, switching from an integrated video card to a discrete one is not always correct (and some games, in principle, cannot be made to work on a discrete card without running them from another OS).

However, the second OS can also be just as a backup to save nerve cells and the TIME when the main one refuses to boot

Below, using my small example, I will show you how to install the second Windows OS (in addition to the main Windows 10, Windows 8.1 will be pre-installed - of course, all this happens without data loss, and you can work with any of the systems!).


The content of the article

  • 1installing the second Windows OS
    • 1.1 STEP 1: Preparing the partition for the new OS
    • 1.2STEP 2: Creating a bootable USB flash drive, disk
    • 1.3STEP 3: Installing the OS
    • 1.4STEP 4: Boot setup (default OS selection)

Installing the second Windows OS

STEP 1: Preparing the partition for the new OS

And so, first of all, you need to create another partition on the current disk for the second Windows OS (if you have two disks, this step can be omitted). It is quite simple to do this with


1) To open disk management, press Win R, and in the window that appears, enter the command diskmgmt.msc

2) If your current Windows OS does not boot, then you can start disk management using LiveCD.

Disk management

Next, we need to ‘take’ some free space from some disk for another partition. In my example below, I will ‘take away’ some space from the disk on which the current Windows OS is installed:

  • to do this, right-click on the disk partition, and in the menu that appears, select’Compress volume’ (see example below).

Compress the volume

After you specify the size of the partition in MB - usually you need to allocate at least 30 GB for the second OS (this is about 30,000 MB)!

An important moment!

The data on the disk (files, directories, etc.) are not deleted during this operation, and do not disappear anywhere. The place for the new section is ‘being taken’ from free (unoccupied).


After performing this operation, you will have another partition on the disk - it will be marked in black (because it has not been formatted yet). To fix it - click on it PCM and select in the menu’Create a simple volume’.

Create a simple volume

Next, agree to formatting (important: formatting is not the whole disk, but only the new partition, which is still ‘empty’).

Formatting a new volume

Preparation is complete!

If everything went smoothly, you will have another disk partition in ‘My Computer’ (see the example below). We can move on…

A new section has been created


STEP 2: Create a bootable USB flash drive, disk

If you already have an installation flash drive (disk), you can skip this step.

To create a bootable USB flash drive for Windows 10 - in my opinion, one of the easiest ways will be to use the utility from Microsoft (note: after clicking on the link - click on’Download the tool now’).

Then, after launching it, you will be able to create both a USB drive and just an ISO image with the OS in a step-by-step mode.

What you want to do

Download the ISO or prepare the flash drive immediately

If we are talking about other Windows OS (7/8), then creating an installation drive boils down to:

  • search and download an ISO image from the desired OS,
  • its correct recording on a USB flash drive/disk (I have about this

Setting up WinSetupFromUSB to write a UEFI flash drive.


STEP 3: Installing the OS

Now restart the computer (laptop) and call

If the boot drive was recorded correctly (and no one changed the BIOS settings), you should see a menu in which you will be prompted to boot from it (in my example, this is ‘USB Hard Drive…’).

How to boot from a USB flash drive or external HDD -instructions for beginners


If your drive is not displayed in the boot menu, go to the BIOS settings and check whether USB boot is enabled (usually this option is called as ‘USB Boot’, see the example below).

If the disk is not visible, check whether USB booting is enabled in the BIOS

Instructions for working with BIOS

I do not stop at the BIOS settings in the article anymore (we will assume that the download from the installation media was successful and the installation started …).

Booting from a USB disk - OS selection

After selecting the language and agreement with the license terms, select’Install the OS for advanced users’, and then specify the disk that we created in step 1 for installation.

Note: Some steps from the OS installation have been omitted because they have no practical value…

Selecting a disk for installing the second OS

During the installation of the second Windows OS, the computer will restart several times, you will be asked to specify the user name, set network settings, etc. (depending on the OS version that you are installing).

Personalization - OS configuration during installation

When Windows is installed, in My computer you will be able to see all your disk partitions (including the one on which the main OS is installed). In general, the task is completed…

The OS Is Installed


STEP 4: Boot setup (default OS selection)

When you have 2 (or more) installed on your computer (laptop) Windows OS - every time you turn on the device, you will have a menu with a suggestion to choose which one you want to download. See the screenshot below (

Select the OS (how the menu will look when you turn on the PC)

This is not always convenient, especially since usually one of the operating systems acts as the main one, and by default it is exactly what you need (and the second one is rarely used as a backup).

In general, this moment can be adjusted, and make turning on the computer more convenient and faster. To do this, open the properties’My computer’, as shown in the example below.

Computer properties

After that, go to the tab’Additional system parameters’.

Additional system parameters

Next, open the boot parameters and recovery.

Download and restore - parameters

Now you can specify which of the Windows will be loaded by default, and how many seconds the menu with the OS selection will be displayed (by the way, it is most convenient to set the menu display to 1-2 seconds. - this is quite enough to choose from, and at the same time will not slow down the PC turning on).

The system loaded by default


That’s all on the topic so far…

Additions are welcome (thanks in advance!).

Good luck!

First publication: 11.07.2019

Adjustment: 11.06.2020

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