Step 1 – Enter your computer’s BIOS
You first need to make sure your computer is set to boot from your DVD drive or from USB. Insert your DVD or USB installation disk and restart your PC. You may find that your PC has a special boot override menu, which you can access with a key such as F10; look out for the message while your computer starts. If this is the case, press the key as soon as the message is displayed, then select your DVD drive or USB stick to boot.
If you don’t have a boot override menu, you’ll need to go into the BIOS or UEFI Setup program, which is where you change some of your computer’s more low-level settings. The right key to enter Setup varies from PC to PC, but is usually Delete, F2 or F10, and you’ll need to press it almost immediately after you turn your PC on or restart it. If you look carefully, you may see the relevant key displayed onscreen as the computer turns on. Some more modern laptops, such as certain Lenovo models, have a special button to enter the Setup program, which you’ll most likely find next to the power switch. Setup menus vary widely in look and layout, but all follow a similar logic, so if you look carefully you’ll be able to find all the options we mention in this guide.
Step 2 – Set your computer to boot from DVD or USB
Once in Setup, find the Boot section. Now change the boot order to put the device you want to boot from first; this will be DVD or USB, depending on your installation media type. Bootable USB flash drives are sometimes listed as hard disks. If this is the case you’ll need to set ‘hard disk’ as the first boot option, then go into the hard disk boot order sub-menu and put your USB boot disk at the top of the list. Find and select the Save and Restart option or equivalent. Your PC should now boot into the Windows 10 setup program – you may see a message to ‘press any key to boot from USB’, so do so.
Step 3 – Choose the Windows 10 clean install option
Once you’re in the Setup program, select your language, time and currency format and input method, and click Next. Click the Install Now button. Enter your Windows key if prompted, and read and accept the software licence. In the next screen, select ‘Custom: Install Windows only (advanced)’.
Step 4 – How to find your Windows 10 license key
At this point you’ll be asked for your licence key. What you put it, depends on the type of Windows 10 that you have, but we’ll explain how to deal with everything here.
If you’re already on Windows 10 and want to know your license key, you can always download ProduKey and extract your Windows 10 product key from there. Write this down on a piece of paper or save it to an external drive.
Step 5 – Select your hard disk or SSD
What you’ll see in the next screen depends on whether you’re installing on a blank disk, or whether your disk has had an operating system installed on it previously. If it’s a blank disk, you’ll be shown a drive with ‘Unallocated Space’, so just select it and click Next. Windows will then start the installation process.
If your disk has had an operating system on it previously, or if you have more than one hard disk in your PC, you’ll be shown a screen with several disks and partitions. The disks will be called ‘Drive 0’, ‘Drive 1’ and so on, and if a disk has previously had a Windows installation it will be split into partitions with labels such as ‘Recovery’, ‘System’, ‘MSR’ and ‘Primary’.
Before you install Windows 10 you’ll need to delete all these partitions, by selecting each one and clicking the Delete icon. This will erase all data on the partitions, so quadruple-check that a) you’re deleting partitions from the correct drive and b) that you’re absolutely sure you’ve already backed up everything you need.
Bear in mind that this may also delete your manufacturer’s recovery partitions, so you won’t be able to go back to your previous operating system. Once you’ve finished deleting partitions, make sure the drive you want to use for your Windows 10 installation is selected and press Next to install.