Been there, done that, got the T-Shirt. 

sfc /scannow tells me it's found and fixed some errors... every time I run it.
chkdsk  (read only) tells me I should run chkdsk /scan to id and queue the errors its seen for repair
chkdsk /scan says...
"Windows has scanned the file system and found no problems.

"No further action is required."

All from an elevated command prompt, obviously.

dism /online /cleanup-image /scanhealth...
[==========================100.0%==========================] No component store corruption detected.

The operation completed successfully.

Attempting to update to 20H2 throws up an error 0x80242016, which is new.
For Quality Updates the error is 0x800705aa, which was the original problem.

When I eventiually get some free time I think I'll have to build that new PC I bought the components for, and just cannibalise my old graphics card instead of waiting.  The problem is finding the free time and the concentration required at the moment.

One more idea: make yourself another account with admin rights and log into it. If the problem goes away, the issue is with your old profile which you can delete after rescuing icons, documents etc. Profiles sometimes go bad while the main Windows system remains good.

Something actually worked first time for me, after it had fallen over, obviously.

One of my Synology NAS drives advised me that life would be a happier, safer, thing if I deleted my named "Admin" account and created another account with a different name, that had all of my admin privileges.  This actually seemd like a decnt idea so I set about doing just that.  Of course, after setting it all up I hit he "save" command and everything froze up, and I was eventually left in the position of having no accesssible account/working password whatsoever.

After a quick trawl (I know this is boring, but it might be of use to osmeone else one day) of t'internet I discovered that the one and only method of correcting this was to use the dreaded paperclip-in-tiny-hole method.  i.e. a complete reset.  Many and various were the scare stories about losing every setting you'd made, and some you probably hadn't, so I was set for major battles.

Paperclipped hole, rebooted NAS, entered "find.synology.com" in the address bar, and it duly found both my drives.  Logged in to the dodgy one using the name "admin" with no password.  Got in and got the option to reset the password (it actually already had the user-name I'd chosen before it failed) gave it a password via LastPass and Robrt's your father's brother.

All my settings were there and Volumio is now kicking out a nice bit of Del Amitri.

I think it probably all went so well because there was minimal interaction with Windoze required. 

Windows 11 coming soon 😉

Obviously it'll lbe called Windows 10. I distinctly remember Micro$oft telling us that Windoze 10 was the final iteration and everything else would just be built on Windoze 10.  No new Windows OS is going to be released they said. Existing Windows 10 will keep getting updated. Hence, there will be no Windows 11, they said.

Maybe, in keeping with Microsoft tradition, they publicly released a bug-ridden beta statement then? 

Link not working for me, Mike.  Was it this oine?

www.theverge.com/2021/6/14/22533018/microsoft-windows-10-end-support-date

Dusted off my mum's Lenovo laptop yesterday.
After the H2 2020 update it had become totally useless. 99% CPU, 100% disk. All occupied by Windows processes.
Everything from logging in to shutting down was taking many minutes for each task.

I had bitten the bullet on my 2 Lenovo laptops which suffered the same fate and installed a SSD drives - all problems solved.

My mum got a cheap Chromebook - much more in keeping with her needs and fast.

I tried to update her old laptop to latest Windows 10. After 6 hrs gave up.
Did a system reset, no need to back up. She had no apps or SW loaded. Just used Edge browser.

It went back to 1909, took ages, overnight and into this afternoon - that's how slow H2 made it.
Once done it absolutely flies again.
Processor drops to 1 or 2% when not doing anything. Disk the same.

I'm going to use it as my Nadja SW and HolmImpulse (measuring mic) SW hifi setup PC, and have blocked further automatic W10 updates. Should be labelled performance destroyer updates).
Sticking with 1909 until end of life.

#1 - I wouldn't be without a Chromebook in my arsenal. They are perfect for what they're designed to do, as your mum is no doubt finding out.

#2 - Nothing is ever Micro$oft's fault.  Everything is the fault of every other company for not pre-designing software, firmware, and hardware, ready to have a bug-ridden, lump of bloatware thrown at it. I thought everyone knew that. 

I'm sure MS knew exactly what they were doing releasing an update that would be incompatible with huge numbers of existing HW out there.
Many would be frustrated bin and buy new.
A fraction would buy SSDs and clone HDs, especially considering how glacial the pace was before you could boot from the new SSD. Another fraction would go back to 1909, and sail off into the sunset🙂

I need Windows or 100% emulation to run the SW to set up Najda, measuring mic system, and run things like Horn SW simulation progs. Written and maintained on W7 by diyaudio star David McBean!
For this I can't replace Windows easily.

This particular laptop won't even be on a network from now on, so not a risk.
It has AMD processors.

However, I still have a Lenovo x200 (pro model) that I use daily, and it can do all of the above and be on the latest W10 SW my having changed the HD for SSD.
It is built like a tank, started out on XP, yes that's how old it is.
It's fast and reliable. I particularly like the above screen keyboard illumination light. Good on 'lights dimmed' aircraft and the bedroom🙂
The finger print reader gave up some years ago though.
As did the wifi module. Easily replaced.
Battery life is pretty bad though. Always plugged in.

So, I suppose getting 10 or more years or of a laptop isn't bad😂