I am using my Lenovo T420S now since more than four years. This notebook is still comparable to current machines that are now on sale. It is equipped with a I7 processor and 16GB of RAM. In addition I added two Samsung SSDs during the years. I haven´t found any significant better notebook of that quality level since I started to look for a new one in this summer. So I decided to still stay with the T420 since there is a lot better one on the market that is worth its price. Best on that decision I had to trying to get Windows 10 working on that machine.
After several (> 10) tries I was finally able to upgrade to Windows 10. Me was confronted with an always occuring 0xC1900101 – 0x20017 error, after the system rebooted for the first time during installation (before the actual upgrade starts). In my case, the T420 rebooted and a start up screen with the Windows logo is shown. After a couple of seconds a single white dot was shown in the lower middle of the screen (should have been a loading spinner). After rebooting, Windows 7 is restored and the following error code is shown:
To avoid a long try and error marathon for you, you just might have to follow the steps I am listing below. It might be, that not all of the steps are necessary to perform. I am sorry, but I tried several steps with each installation attempt. So, you can just check, if a subset helps you.
- Use the windows media creation tool to download the Windows 10 upgrade directly to an USB stick from which the installation can start later on.
- When installation starts and you are asked if you would like to update the installation software, you should do it.
- Finally I went to change some BIOS settings and those are the ones that enabled me to install Windows 10.
- Config > Display
- Boot Display Device: Thinkpad LCD
- Graphics Device: Discrete Graphics
- OS Detection for NVIDIA Optimus: Disabled
- Config > Power
- Intel Speedstep technology: Disabled
- CPU Power Management: Disabled
- PCI Express Power Management: Disabled
- Config > CPU
- Core Multi-Processing: Disabled
- Intel Hyper-Threading Technology: Disabled
- Security > Memory Protection
- Execution Prevention: Disabled
- Security > Virtualization
- Intel Virtualization Technology: Disabled
- Intel VT-d Feature: Disabled
- Security > I/O Port Access
- All to disabled, expect of Ethernet LAN and eSATA Port to update the Windows installation software before the update
- UEFI/Legacy Boot: Both
- UEFI/Legacy Boot Priority: UEFI First
- Reserve memory for UEFI Boot Manager: Enabled
- Config > Display
With theses settings in the BIOS I was now able to install Windows 10 to my machine. After the installation finished, you can set back all settings to their original state, expect the Config > CPU > Core Multi-Processing that needs to stay in the state „Disabled“.
From my current point of knowledge, the Core Multi-Processing is not effecting the actual active cores of the CPU, but is just some kind of „combining“ multiple cores to process a single thread. On my notebook this isn´t affecting the speed of the machine at all.
After installing Windows 10 I recommend to install software updates from Lenovo to your system. There are for instance new drivers for the NVIDIA Optimus.