 Hello everybody! This video is about installing two working operating systems on one computer. I mean having a Windows 7 as the main system and Windows 10 as an additional system. If necessary, you can use the method I will describe to install another copy of Windows 7 on your computer. You may need to install another operating system on a modern computer if the current operating system can't help you in a certain situation or you need it for certain kind of work. At the same time, it is important to have the first main version of Windows. The disadvantage of having two Windows in one computer is impossible errors during the installation. Damaged boot record, failure in both systems due to wrong actions and, as a result, loss of important data. So let's begin. Our computer has Windows 7 installed. And there is another hard disk connected. Let's install Windows 10 there. Not to get confused, let us rename the first disk to be Windows 7, and the other, where a newer version will be installed, Windows 10. It is no accident that we are installing Windows 10 to the other hard disk. This is the right way. Also Windows 10 should be installed with the bootable media, having changed the boot priority in BIOS or UFI, and not from within the working operating system. Otherwise, Windows 10 will automatically run the installation by upgrading the already running Windows 7. Watch another video on our channel to see how to enter BIOS or UFI and boot your PC from the USB drive. You'll find the link in the description. Then, run a bootable USB drive or a Windows 10 installation disk, which you can buy or create. Watch another video on our channel to see how to create a bootable USB drive to install Windows 10, 8 or 7. You will find the link in the description. In the Appearance Setup window, set the language and time format. Next. Install Now. Setup is starting. Accept the License Agreement. Next. Select the installation type. The most important thing is not to click on Upgrade accidentally. It means installation onto the existing operating system, and we don't need it. Choose Custom. And the system will ask you to select the disk where to install Windows. That is what we need to have two operable Windows and one computer. Select Disk D having 75 GB of free space that we prepared beforehand and click Next. I would like to point out that a computer with UFI should have GPT-style partitions, because Windows cannot be installed on an MBR disk or of a computer with UFI. If you turn out to have an MBR disk, it can be converted into GPT with third-party software, or you can reinstall Windows 7 converting the disk into GPT. Then begin Installation of Windows 10 as the second operating system. After that, the process of Windows installation begins. In fact, installing Windows 10 as the second system is no different from clean installation or upgrading the system to Windows 10, so I won't be describing each of them. You can watch another video on our channel to see how to make a clean installation of Windows and learn about possible installation problems and ways to fix them. You will find a link in the description. After making all additional settings in the end of the installation process, the second system will boot. Restart the computer. As you can see, the system which we installed second is now the default operating system. It will boot automatically when the timeout is over. I'd like to add some words about the window where to choose the version of Windows to boot. Different depending on what is your default system. If it is Windows 7, you will see an old style screen with white letters against black background. If it is Windows 10, there will be icons with names of the operating system on the blue field, like the advanced startup window as we see now. If you need the first system to be the default system, in our case it is Windows 7. Here is what you should do. Let's start the system configuration menu. To do it, press Windows plus R and enter msconfig. Ok. Go to the tab Boot. We can see that Windows 10 is the default system. Select Windows 7 and click on Set as default. And then there will be a line next to it saying Default operating system. By the way, the timeout duration can also be modified in this menu. For example, let us set it to one minute. That click Apply and OK. After that, the system will ask to restart the computer for the changes to take effect. Start. After that, Windows 7 will boot by default. And if you need to boot Windows 10, you'll be able to choose it. Please note, the window to choose one of the operating systems has changed. If you no longer need the other system after some time, or you need to delete one of them, do the following. Boot the windows you want to have. Press Windows plus R and enter msconfig. Ok. Go to the tab Boot. Select the operating system you want to have and click on Set as default. The corresponding status should appear next to it saying Default OS. After that, select the operating system you want to delete. In our case, it is Windows 7 and click Delete. Then click Apply. Ok. Restart. The computer will restart this time without options to select an operating system. The system we decided to keep should boot at once. In our case, that is Windows 10. What should you do with all the system files? The easiest way is to format the disk or partition where it was installed. It is best done from the Disk Management menu. To do it, go to Disk Management. Right-click on the necessary disk, select Format, Ok, and Ok once more. Remember that all data stored in the deleted operating system will be gone. So if there is any information you will need, make sure you save it to another disk before the installation. If you lost some files as a result of installing, uninstalling, updating, or resetting Windows, you can bring them back with Hetman Partition Recovery. To see it on video, find the link in the description. If you liked this video, click the Like button below and subscribe to our channel to see more. We'll be glad to answer any questions in comments. Thank you for watching and good luck.