How to completely clean install Windows 10 on a UEFI PC

With Windows 10 I generally do recommend to simply upgrade which preserves your apps (modern and desktop), data and settings. In contrast to previous Windows versions the Win 10 upgrade is robust and has worked fine for me on several machines, so I consider a clean install not being worth the time needed.

With my Surface Pro 3 (SP3) however I wanted to do a clean install, including removing Windows 8.1 partitions no longer needed. A Win 10 upgrade from Win 8.1 left my Surface with the partitions shown in the picture below. I could not find any reliable information on which partitions are safe to delete.

PartitionsAfterWin10Upgrade

Partitions after upgrading from Win 8.1 to Win 10

A clean install as described below removed 2 unneeded partitions and freed 5+ GB SSD space:

PartitionsAfterWin10Clean

Partitions after Win 10 clean install

Clean Win 10 install

For a really clean Win 10 install one must boot from installation media. Starting Win 10 setup from within Windows does not allow to remove unneeded partitions.

I used the following steps to do a clean install:

  1. Download Windows.ISO
    via Windows 10 using the media creation tool.
  2. Create UEFI-bootbable USB stick
    via Rufus.
    Rufus
    (select GTP partition scheme for UEFI, FAT32, the Windows.iso downloaded).
  3. Change boot order
    on SP3 to USB -> SSD
    via holding volume-up key while releasing the power button.
  4. Boot from USB
    which automatically starts Win 10 setup.
  5. Delete all partitions
    from within Win 10 setup.
  6. Complete Win 10 install.
  7. Run Windows update.
  8. Change boot order back to SSD only.

Obstacles

USB sticks for booting with UEFI must be formatted as FAT32. The current standard Microsoft tools allow to create NTFS only. Thus I used Rufus.

My SP3 would not boot from a USB stick.
I worked around that using Advanced Startup Options:
Win10AdvancedStartupOptions
Later I found that I had disabled “Boot from side USB” in UEFI advanced security settings. After enabling this my SP3 boots fine from USB.

Some Hints

My Win 10 did activate automatically. When asked for a license key during setup I always skipped. I do not know if the Win 8 license key was stored in UEFI or if it was stored in my MS account because of a previous Win 10 upgrade.

After Setup and before installing any Windows updates wireless internet worked already. To speed-up updates I re-plugged my USB Ethernet adapter which promptly caused Win 10 to install a driver for it.

Device manager showed many device drivers missing. I simply ran Windows update. After all updates were installed, device manager no longer showed any drivers missing. There was no need to manually download an install the Surface Win 10 driver package.

About Peter Meinl

IT Consultant
This entry was posted in Computers and Internet and tagged , . Bookmark the permalink.

2 Responses to How to completely clean install Windows 10 on a UEFI PC

  1. David Prows says:

    Does Bit Locker work after doing a clean install?

    • Peter Meinl says:

      Yes BitLocker works after a clean install. If you want to keep data that was encrypted with a previous installation (e.g. you encrypted the SD Card in your Surface) you must export your BitLocker keys from within this previous version before the clean install and supply them when asked by the new version. Alternatively you could decrypt everything first: less complex but may take a long time.

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