Select the Primary partition from multiple partitions, and click Next.

Select the unallocated drive list Click New > Apply > OK.

Select the drive and then click Next.

Click Custom: Install Windows only (advanced).

To do so, check the box in front of “I accept the license terms”. Just wait for a while the system prepares itself to copy files.Make sure to enter the correct edition if you choose the wrong edition then, you would need to perform a clean install again. Now setup will ask you to choose the correct edition of which you have a License, either Home or Pro.Otherwise, click on “I don’t have a key” or “Do this later.” Now, Windows 7 set-up will ask you to enter the Product Key if you have a Windows 10 product key, proceed to enter it.Next, you will be asked to select your Language, Time, and Keyboard method, and after configuring all these things, Click Next.Then the Windows logo will appear on the screen for a while, if you see the animated dots it means everything is fine.You see a screen with a list of drives, choose the one you inserted/plugged in, and hit Enter.Restart your PC, and while booting, before the Windows logo, tap the Boot Menu key to open it.After completion, Rufus will ask you to restart the PC.Now, click on the Start button and wait a while to finish.

Make sure to keep all the default settings as it is.

Now, open Rufus to create bootable media for Windows 7.

Now follow the following steps to clean-install Windows 7 using the ISO file, If you have your Windows 10 ISO File ready to update your system to Windows 10 Latest Update, all you have to do is boot from the disc or USB thumb drive to start the setup.

There is a checkbox above the download button if you check that, your Windows 7 ISO will be downloaded via a web browser.