It is mentioned here:

https://www.dell.com/community/Laptops-General-Read-Only/Dell-Inspiron-14Z-5423-windows-10-booting-issues/td-p/4567711/page/4

And I've read a lot of posts where people had bricked their 14z by upgrading to windows 10. I guess a lot of people didn't bother to try and downgrade to A12.

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@nerovectra wrote:

It is mentioned here:

https://www.dell.com/community/Laptops-General-Read-Only/Dell-Inspiron-14Z-5423-windows-10-booting-issues/td-p/4567711/page/4

And I've read a lot of posts where people had bricked their 14z by upgrading to windows 10. I guess a lot of people didn't bother to try and downgrade to A12.

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1. That thread is seven years old, from 2015. Windows 10 was new in 2015. Now it is mature and has excellent driver support. That old thread is no longer relevant.

2. You cannot brick your computer by upgrading to Windows 10.

3. Windows 8.1 will be at End of Life in less than one month. At that point it will be unsupported and insecure. It will not receive security patches, so it should no longer be used on a PC connected to the Internet.

I suggest that you update to Windows 10. Do the free upgrade: https://www.zdnet.com/article/heres-how-you-can-still-get-a-free-windows-10-upgrade/

After upgrading, check to see if Windows 10 is activated in Settings | Activation. If it is, then you can perform a clean install of Windows 10 and it should activate automatically.

Alternatively, if you have your Windows 8.1 Product Key, you may be able to perform a clean install of Windows 10 and manually enter your Windows 8.1 Product Key.

Before doing any of that, though, it would be worthwhile to install the newer BIOS, as @JOcean suggested.

Thank you for your replies. This means that it would be a coincidence that many of these devices didn't survive the windows 10 upgrade. And I think it is tricky to assume that the fact that there are newer builds available, means that it would be "more" compatible. The device now works flawlessly. I would like to keep it that way. :-}

@filbert is spot on and the OP may have also had a BIOS update that caused the problems. To blame Windows 10 would be analogous to getting a haircut then breaking an arm and blaming the haircut for the fracture. 

Maybe it is impossible to brick your device bij upgrading to windows 10. But fact is that a lot of people, if not all owners(?), had to downgrade to A12 to get their device usable again. If not necessary, I wouldn't risk it. I hope there is someone who can state that the recent bios updates are compatible with windows 10.

As many Windows 10 upgrades failed at BIOS A13, wouldn't it be a better idea to upgrade to windows 11 and update BIOS to A16 afterwards? At least then you know for "sure" that it's a BIOS issue if it fails, and need to prepare to flash A12 again.

Your laptop is over ten years old. It does not meet the requirements for Windows 11. While there are ways to get around Microsoft's minimum requirements, you would face two issues:

1. Microsoft has stated that at some point they may enforce the requirements so that systems that don't meet the requirements would no longer receive updates for Windows 11.
2. Windows 11 is likely to perform poorly on your old system. Windows 10 should run better on your system.

If it were my system, I would update to BIOS A16, which is labeled as a "Critical" update to address a "security vulnerability".

I was brave enough to try. I updated BIOS to A16 and upgraded to windows 10. Eitherway I was lucky or A16 really has no issues with windows 10. To anyone who has to decide to leave windows 8.1: it's worth the try!

Happy to hear it worked out for you!