Build 10240

Hi, you are now 2 major builds behind, as you have just the first release of Win 10. 10.0.10586 came out in Nov 2015 and 10.0.14393 in August this year, still being delivered to customers.

That suggest you have Windows update disabled, or are not connected to the internet, or Windows update is not working.

So you can either fix those problems, if any, or manually download the current iso and burn a DVD or USB disk manually, or directly create a bootable medium using MS's media creation tool, or just mount the iso and proceed from there.

Hello, suggest you research the web e.g.
Windows anniversary edition problems
- MS is working on a number of issues that have affected a good number. Others have no problems with it.
Note the changes - some have complained about start menu changes. (Win 10's start menu is relatively useless anyway- my opinion and that of a few others here).

You may wish to wait another month or so before updating. Only one problem has supposedly been fixed in a recent update.

You can search the web as to how to get it.
I searched for you thus:
how do I manually download the anniversary edition
e.g.
How to get the Windows 10 Anniversary Update | Windows Central
- see section on media creation tool
OR
if you want an iso- from the Tutorial section here I found you:
Windows 10 ISO Download - Windows 10 Forums

Keep a Win 10 physical bootable medium- it can be useful for repairs.

Before upgrading, use disk imaging to secure your system. Disk imaging is sthg everyone should use-
- if your hard disk fails
- if your PC becomes unbootable
- if you have an unresolvable technical problem

Having a recent image of your disks/partitions means you can quickly restore your PC without technical help.
Also the images are a full data backup.
Recommended: e.g. Macrium Reflect (free) + its boot medium + external storage.

You can ask MS for the 10240 iso, they will provide it with no problem. Sure, the tech (may) try to persuade you to get the latest build. Remember, your the customer who has previously installed the 10240 and you did not get the required CD/DVD with the product. Also your already have a working win10 computer or one that may need repair (meaning you are already partitioned and not looking to do a clean install) and should have received the "original" product that came with program. (aka CD/DVD/iso).

If this fails, point them to the "History of the Win 10 Builds(See link below)

https://www.google.com/url?sa=t&source=web&rct=j&url=https://technet.microsoft.com/en-us/windows/release-info.aspx&ved=0ahUKEwjdzIWBvIHPAhVKOyYKHV08AowQFggfMAI&usg=AFQjCNFq6xzapach_P99BcDjySnsPct4Ng&sig2=i jybGI7EHiJpUTPxMEX87w

This list provides the 3 Builds/Rings and upgrades(KB docket # and the latest release dates for the build type). The current Builds " at this time" for the different architectures are as follows:
Build 10240(RTM)
Build 10586
Build 14393

IMO, I think this is "one" of the reaons why so many are reinstalling (new partitioning).

Let me provide an example why I believe this to be true in many cases.
Your computer has bulid 10586 previously installed, the efi partition drops out (for an unexplainable reason)...your now repairing your computer(manually adding the efi partion back in).... your C: drive has the Windows build 10586 program, you call for an iso link but didn't mention which iso link and they provided you with iso for 14393 build....now, heres the question to you? Is that a compatibility issue? I would say so....

Software is sensitive to communication. If, I'm holding my hand out to you as a greeting as taught (aka programmed) but you extend me a glass of water instead of shaking my hand, then that's a send/receive (signal or as we say an expectancy) problem...(this part is what I call conflict resolution)

If you've found yourself frustrated (as most have found themselves experiencing with the need to reinstall) Consider this theory of mine. Hope you find some peace.