Windows users are always recommended to backup all data from the hard drive before beginning to install or reinstall the operating system. This is because, more often than not, we format the drive containing existing Windows 10 or Windows 7 installation before performing a fresh install.
Formatting the drive before installing Windows means we need to backup all documents, pictures and other important data from the desktop. And if you have installed tens of programs, you probably even need to make a note of all installed programs to download and install all programs quickly post the Windows installation.
The fact is we can install or reinstall Windows 7, Windows 8/8.1 or Windows 10 operating system without formatting or erasing Windows drive provided that the drive has plenty of free space to accommodate the new installation. In other words, the drive containing existing Windows installation must have a minimum of 16 GB for 32-bit and 20 GB for 64-bit free space in order to perform a fresh installation of Windows without erasing the drive.
When you install or reinstall Windows without formatting the drive, Windows setup moves the existing Windows installation to a new folder called Windows.old, meaning you don’t need to backup all data before installing Windows. After performing Windows installation or reinstallation, you just need to open up the Windows.old folder to recover your data before deleting the same to free up some disk space.
Follow the given below instructions to install or reinstall Windows without erasing or formatting the drive. And if can’t locate your Windows product key, please follow our how to reinstall Windows without the product license key to reinstall Windows without the product key.
Install Windows 10/8/7 without erasing previous installation
Step 1: Make sure that you have at least 16 GB (for 32-bit installation) or 20 GB (for 64-bit) of free space on your existing Windows drive before continuing further. If you don’t have the required free space, you can try extending the existing system partition or disable hibernation.
Step 2: Connect your bootable Windows installation media to your PC, make necessary changes to BIOS/UEFI to boot from DVD/USB, and then boot from the bootable media. You can go through our how to create bootable Windows USB or how to install Windows from USB guide to prepare your bootable USB drive.
Step 3: Follow the on-screen instructions until you see the drive selection screen where you need to select a partition to install the operating system. In this step, in order to install Windows without erasing the drive, simply select the drive containing existing Windows installation and then click Next button.
You will see the following dialog box:
Simply click on the OK button to proceed installing Windows by moving existing installation to a new folder called Windows.old.
Step 4: Follow the on-screen instructions to complete the installation. Once the installation is done, navigate to Windows drive and open up Windows.old folder to access your data from the previous installation.
Once you have recovered all data, follow our how to delete Windows.old folder to free up GBs of free space guide. How to make your USB device bootable without formatting guide might also interest you. That’s it!