Older Lenovo T420 laptop will not boot to Windows

I am trying to help out my brother with his old Lenovo T420 laptop. It came with Win7. I upgraded to Win10 back when free upgrades were offered. All went well. Now several years later he asked me to have a look at it because it will not boot to Windows.

I tried to repair. I tried to go back in time to a system restore point long ago. Still would not work. It would not even allow me to boot in Safe Mode. I am able to get a command prompt. I am little confused as the drive letter is X: . Please don't laugh. I just have not seen this before.

I could do a fresh install, no problem. Problem is I don't have a WIndows 10 key from the upgrade. If it was even a possibility I can no longer read the Windows 7 key on the bottom of the laptop either.

So I am afraid to wipe it and start over for fear of not being able to activate. Can someone offer some advice? Is

If you at any time upgraded from windows 7 or 8 to 10 on the computer then there is a license on the Microsoft servers.
Once on the Microsoft servers a product key is no longer needed when performing a clean install without major hardware change.
Making backup images is highly recommended in Ten Forums.
Many have free and pay versions: Acronis, Aoemi, EaseUS, Macrium, Paragon, etc.
Then when there are problems you may be able to restore an image.

If there are no important files on the computer the quickest method may be a clean install.
This however requires the reinstallation of drivers, applications, and the customization of Windows.
In addition to losing files, bookmarks etc. are also deleted.

Options that you can attempt before clean install are:
a) startup repair
b) system restore
c) reset save files
d) reset save files equivalent (using a windows 10 iso)

https://support.microsoft.com/en-in/...covery-options

Run Startup Repair in Windows 10 | Tutorials
System Restore Windows 10 | Tutorials
Reset Windows 10 | Tutorials

Download Windows 10 ISO File | Tutorials
Download Windows 10

Clean Install Windows 10 | Tutorials

zbook said:

Making backup images is highly recommended in Ten Forums.
Many have free and pay versions: Acronis, Aoemi, EaseUS, Macrium, Paragon, etc.
Then when there are problems you may be able to restore an image.

Thanks for the key explanation. I have often wondered about that. It was just now that I have run in to the problem. Based on that I am currently performing a clean install.

Regarding the backup images. I another question that has been around for a while. What is the difference between all of Acronis, Aoemi, EaseUS...... and the one you can perform just using the Windows 10 OS?

The Windows methods are being depreciated.

There are multiple methods to protect and restore files using images.
Some of the software have a quicker learning curve and others provide more options once you learn the methods.
It's best to open a thread in this forum: Backup and Restore - Windows 10 Forums

Many in Ten Forums use Macrium:
Macrium Software | Your Image is Everything
Backup and Restore with Macrium Reflect | Tutorials