Win 10 stuck on build 10240

Not unless you wish to do a clean install and wipe everything, or use 'Repair your computer'.

Please go back to post 2 and follow from 4 which is the next step I believe.

Observe all preparatory precautions, including creating a disk image which is not obligatory, but which you would be kicking yourself for not doing if your PC becomes unbootable and is strongly recommended and practised routinely by contributors here- for which you need to download and use eg. Macrium (free) or another such program.

There is a tutorial and videos on this site for Macrium, there is a large help file and youtube videos and more on its own site.

You also need a large enough external storage medium (typically HDD) say 2x as large as the used data you are backing up.

dalchina said:

You also need a large enough external storage medium (typically HDD) say 2x as large as the used data you are backing up.

Well, you only need enough spare space for size of data backed up (and less in fact as compressed). Sure it is GOOD ADVICE to use a drive with plenty of spare space to allow mutiple backups, and to avoid fragmentation if space is really tight, but not essential.

I only say this in case OP thinks he/she would need a new drive when perhaps he/she would not.

True, you can do one base image and it will be less than the used space- out of habit I used the figure I use for routine use of disk imaging with a number of differential images as well as the base image. I have 1.25 Tb in my PC and found a 1Tb backup disk a bit tight after some time.

3. Separate downloading the iso and the update and installation process.
Download it manually:
Download Windows 10 ISO File Windows 10 Installation Upgrade Tutorials

When you have that you can use it repeatedly, and you also have a useful bootable tool for certain repairs if you create a DVD or bootable USB drive.

Create Bootable USB Flash Drive to Install Windows 10 Windows 10 Installation Upgrade Tutorials

You can also burn it to a DVD, if you have a DVD drive, then boot from that. As I have one, that's my preference.

You may prefer these instructions:
Creating a bootable USB drive.

with thanks to @NavyLCDR
To reliably make a bootable USB flash drive from an ISO file, do this:

Plug the drive into a USB port of a functioning Windows PC.

Open a command prompt.
Run diskpart.

Once diskpart is running, enter the following commands in sequence:

list disk
select disk #
- replace # with the actual disk number of the USB flash drive
clean
- this will erase the selected drive, make sure it is the USB flash drive!
create part pri
format fs=fat32 quick
active
exit
exit

Then mount your ISO file.
(By default you can simply right click the iso file, and click Mount. However, Mount will not be available if iso files have been associated with a different program).

Copy all the files and folders from the mounted ISO file to the USB flash drive.

(If stuck you can open the iso with 7-zip, a free program).

Discussion here:
Reinstall Windows 10 from DVD but no DVD drive[/U][/URL]
- includes content of flash drive.

Then you try to do the upgrade, booting normally.

Note: Macrium free is usually good enough for most- one advantage of the paid edition is it gives you access to their forums. You also get the ability to do incremental images (smaller and faster) and some other features I don't recall.

For what? Question can't be answered without understanding the purpose of them... I don't know, sorry. The mrimg files are Macrium image files. The MediaCreationTool is presumably MS's tool for downloading ISOs. The Windows.iso is presumably what you downloaded with that tool.

But any of them could have been renamed in any way at all... so could actually be absolutely anything...!

You're doing well.. when I was at university, we had one derided course added on about microprocessors... and the lecturer told us we'd all be using them one day.

And when I started work, I had to use paper tape- a two pass assembly meant feeding the tape through twice...

8kbytes of RAM on 8 PCBs made up 64kbytes of RAM...