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Windows 10 clean install

10 Jul 2016 - by 'Maurits van der Schee'

In order to keep Windows running smoothly you need to reinstall it every now and then. In this blog post I'll explain how you can make a USB drive to perform a clean install. Booting a UEFI machine from USB (without using legacy boot) may be a bit harder than you are used to.

Get Windows 10 installation media

This is where it is at:

https://www.microsoft.com/en-us/software-download/windows10

On Windows the above link allows you to download the "Media Creation Tool". On Linux on the other hand this allows you to download ISO files of Windows 10. You can use the user-agent switcher to choose either method. Note that the page contents depend on the operating system in the user-agent string and not the browser.

Create a bootable Windows 10 USB drive

Download the Media Creation Tool and tell it create an installation on a USB drive. You need a drive of 4GB or bigger and all contents will be removed. By default it will download the version of the machine it runs on, but when your machine does not boot anymore you may override this setting. After downloading, verifying and writing to your USB drive you can insert can try to boot from the newly created drive. Note that this process may take an hour or even longer, depending on the speed of your Internet connection and USB drive.

Create a bootable Windows 10 USB drive from ISO

You may run Rufus with the following settings:

• Partition scheme: GPT for UEFI
• File system: FAT32
• Check "Create bootable disk using" and point to your Windows 10 ISO.

Other settings may be left to their defaults.

Your Windows 10 key

You actually may not have to enter a valid Windows 10 key as the website states:

If you’ve already successful activated Windows 10 on this PC, including if you upgraded by taking advantage of the free upgrade offer, you won’t need to enter a Windows 10 product key. You can skip the product key page by selecting the Skip button. Your PC will automatically activate later. source

Nevertheless it would not hurt to actually know the key (which can be found using Linux as you can read here).

UEFI boot from USB

Modern Windows computers boot using UEFI. I do not recommend "Legacy boot" or turning "Secure Boot" off. I recommend that you boot the Windows 10 installer from the USB drive in UEFI mode. Getting your UEFI system to boot from USB can often be configured in the BIOS that you can normally enter by pressing F2 during boot. Microsoft writes:

If you restart your PC and your current version of Windows starts, you might have to open a boot menu or change the boot order in your PC's BIOS or UEFI settings so that your PC boots from the media. To open a boot menu or change the boot order, you'll typically need to press a combination of keys (such as F2, F12, Delete, or Esc) immediately after you turn on your PC. For instructions on changing the boot order for your PC, check the documentation that came with your PC or go to the manufacturer's website. source

Some technical facts about booting Windows 10 using UEFI:

• UEFI bootable drives have a GPT partition table.
• UEFI boot searches for a folder named "efi" on a FAT32 partition with "esp" flag (GPT alias for "boot").
• UEFI starts from the file "\efi\boot\bootx64.efi" on that partition.
• UEFI drives have a partition with the "msftdata" flag for the NTFS file system.
• UEFI drives have a partition with the "msftres" flag to store hidden sectors in (res=reserved).
• UEFI boots to a drive that contains a BCD (Boot Configuration Data) store that holds the boot options.

You may use a tool like Visual BCD Editor if you need to do some deep-diving or repairing. Other than that a tool like "gparted" (on Linux) will give you a lot of insight into the inner workings of UEFI booting.

Feedback

Did I miss something? Errors? Report them at: maurits@vdschee.nl. Your feedback is highly appreciated!

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