I changed my user account name and now my laptop is unable to boot up.

Okay. I am kind of on a more sustainable memory now.

Considering I am everything John, Andrew and Guest.

And the course here is that it's Lenovo to blame. You did not actually delete any user files. 

What you have to do is attach the hard disk to an enclosure or a SATA to usb disk. 

You are going to have trouble here. Once you can enter the disk in any other console and look for the disk in your computer. Go to the disk properties. And go to the security panel and click on the advanced options. You will then be required to change the owner. The owner is in the advanced button tad. Use find in order to look for that user computer identities. And most likely use that computers already set up administrator user. From there you will have to check for user changes and the list will change to an addition s- type user profiles. Click on the users profiles and edit or add. Some option should allow you to change that user profile to the administrator on that computer. And that s- type profile should disappear and will be listed as the current administrator profile only. Click okay and wait for the changes. On some occasions not all the files in that folder will change and you can skip the ones that cue the problem. When the windows are closed the process is finished refresh the file explorer page to find the disk contents. Good luck, Pike.

If you upgraded to Win 10 when the free offer was made, you got a digital license that is linked to your Microsoft account. Ever see it at "START, Settings, Update & Security, Activation"...?...

Once you've got that, you need no Product ID ever again. You do need to be installing the same Edition (Home, Pro, etc.) that you had before, is all. But that is automatic. Just be sure to enter your Microsoft account password during the installation process. Here are my tips on the process...

(1) Definitely backup your user files & downloads first because they get wiped in a clean install. I would even say to make a Windows system image backup first (which could restore the computer to its current state), except its current state is pitiful.

(2) If you give it your Microsoft account password when asked, Windows will be activated by the end of the install process. Also, reconnecting to OneDrive, your email account, the Store, etc., is all automatic. Some Windows settings held on OneDrive will be restored & any files you've put there will be accessible. Nevertheless, I would first back those up to external media as well.

(3) The only other password I was asked for was my WiFi password (written on the router). WiFi was automatically all set up afterward. But I did have to reinstall my WiFi printer.

(4) BIOS & other firmware won't be affected by the clean install, but it's best to update them first.

(5) If the drive on which you choose to install Windows has a partition of your own you wish to keep, do not delete it. In that case, delete only the Windows partitions at the "Where do you want to install Windows" screen, & click "Next". I had no extras except two from Dell which I did delete.

(6) Only a few of my Dell/Intel/Realtek drivers needed to be updated afterward. Most just reappeared on their own fully updated. May as well have important ones handy, though, as Greg says in his article.

(7) It's best to do a UEFI install (not a Legacy install) for added security & the benefits of a GPT (not MBR) hard drive partitioning style. To do that, BIOS must be set for UEFI mode. If the computer is capable of it, it must have come that way from the factory. MSInfo32 (type into Search) shows it in BIOS Mode:  BIOS Mode UEFI. In addition, you must choose to boot the Installation media from the UEFI option (if more than one is offered), as Greg says.

It isn't going to be as tough as it sounds. Cortana began speaking after the first 18 minutes, & the installation was completed about 9 minutes later. Here is Greg's article...

https://answers.microsoft.com/en-us/windows/forum/windows_10-windows_install/clean-install-windows-10/1c426bdf-79b1-4d42-be93-17378d93e587

Clean Install Windows 10

Yes I am going to reinstall windows, but don't know the product key. I searched on internet and find that it will automatically verifed my laptop because windows was already activated on my laptop. What do you think?

I already copied my important files from c drive by this way. Now I want to perform a clean install, but don't know the product key. Is it occurs problem after i made a clean install?

It's surprising it dropped out of NetPlWiz yet its name is still Susan. Anyway...

(1) If you need to backup important user files & downloads (in anticipation of a clean install), here is a way. Notepad works very well at a Command Prompt of the Recovery Environment.

(a) Plug in a USB drive on which to copy your files.

(b) Get to the Recovery Environment, & at the "Choose an Option" screen,

     click "Troubleshoot > Advanced Options > Command Prompt".

(c) Enter Notepad at the Command Prompt.

(d) In its File menu, select Open.

(e) Set Notepad to display all file types with its requestor at bottom.

The files you want are likely in the folders at "C:\Users\Susan". Remember to Refresh the screen after a paste. Additional notes...

o  Notepad's left pane has only "Quick Access", "Libraries", & "This PC".

o  Click This PC to switch from C: to the USB drive & vice versa.

o  Double-click a drive or folder in the right pane to open it. Or just select it, then click the Open button at bottom. But ensure nothing is in the filename box, or you get an error message (if it isn't a text file).

o  Right-click a file or folder, & select Copy. That seemed instantaneous.

o  Go to the USB drive, right-click in Notepad's right pane, & select Paste.

     I had an hourglass for just about a minute - or was it two - for 1.3 GB.

o  When the normal pointer reappears, right-click in the right pane, & select Refresh - or I think you never will see it.

(2) Also in anticipation of a clean install, make Win 10 Installation media here...

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

Download Windows 10 - This is always the latest finalized Windows version, currently 2004.

Download MediaCreationTool2004.exe & run it to make a Windows 10 Installation USB drive (or an .iso to burn to DVD). Follow the instructions under "Using the tool to create installation media". As it says, match it to the Language, & Architecture (x64/64-bit or x86/32-bit) of the computer on which it will be used. The Windows Edition to take is "Windows 10", which includes both Home & Pro.

(3) Then, to boot it...

You need to press an F-key during boot to get to the BIOS Boot Menu. If you don't know it...

https://www.sysnative.com/forums/threads/get-access-to-bios-settings-boot-menu-f-keys-hotkeys-by-system-manufacturer-oem.23010/

Get access to BIOS settings & Boot Menu: F-keys/Hotkeys by System Manufacturer (OEM)

Note: That is an informative 3rd-party site. But I know nothing (bad or good) of any downloads or links that are there.

(a) Insert the DVD or plug in the USB Installation media.

(b) Boot or reboot the computer.

(c) Press & hold the F-key at the manufacturer's logo (or at the black screen just before the logo).

     If the key was pressed in time, mine shows activity at the bottom of the screen,

     & the BIOS Boot menu soon shows up.

(d) From the BIOS Boot Menu, choose the "UEFI" option for the media, if offered.

     Mine names the device brand & precedes it with "UEFI:".

(e) If it were a DVD inserted, you get a message to "Press any key" to boot it.

     If not pressed in time, the DVD will be bypassed & Windows will try to boot.

When the Installation media boots, you may select "Repair your computer" instead of to install. That will reboot to its own Recovery Environment at the "Choose an Option" screen.

Or, you may perform a clean install. Want instructions?