Stopping installation of Windows 10 upgrade

I did the stupidest thing. I started the Windows 10 update, choosing to upgrade later thinking I could keep postponing the actual upgrade indefinitely until I was sure my main program would work with it. But what I got instead was a choice of today, tomorrow and the next day only! Can I just shut down my machine and will that stop the whole process? Or 1) will it prevent my machine from shutting down properly? 2) will it install the upgrade the next time I reboot? 3) will it install upon reboot if i do a hard shutdown?

More questions:
I'm told that I can delete the KB3035583 files and that will prevent it. But can I do that at this point? If so, where do I find all of them to delete them? Is it possible to do it when I'm one step away from the update starting (see attached jpeg). I know I can revert to 8.1 within the first 30 days but i will need my Windows 8.1 product key. It came with the machine so how do I find that?

John CarneyReliability Business Tools Analyst IIAsked:
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Tyler BrooksNetwork and Security ConsultantCommented:
As a rule doing a hard shut down when Windows is trying to update is likely to cause major issues with the OS, possibly resulting in a full reinstall. It would be better to either attempt to delete the update so the install doesn't attempt to install or to let it install and if your software doesn't work, roll the update back.

You can delete an update by:

Going to control panel> programs and features> then click the button "View Installed Updates". Select that update and click uninstall, it should prompt you to reboot but choose the option to do it later. Run the Disk Clean up tool and select the Clean up system files after the initial scan. Select the Temporary installation files for deletion. Once they are removed reboot your system and then check for Windows Updates once again.

If that update shows up in the list of update to download, right click on it and select hide.

Systems that have Windows 8.1 have their product keys programmed into the hardware which means that you generally don't need to have the product key to reinstall, and as far as I know you don't need to enter it at all to roll back after installing 10. If you would feel more comfortable having a copy of it you can download Magic Jellybean Keyfinder and it will be able to retrieve the key for you.

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You don't need the Windows 8.x product key. Once the upgrade is done you can just restore the old OS from within Windows 10, as it backs the old OS up. Personally I'd suggest doing the upgrade, and if your software doesn't work properly , you can restore the old OS if necessary.

You can uninstall kb3035583 via the control panel, programs and features, Windows updates.

I'd also rather manually download the correct Windows 10 iso using the windows 10 media creation tool, then extract the contents of the iso and run the setup.exe file to do the upgrade. I've found this to work better and more reliably than when you do the automatic upgrade via the taskbar icon:

Just make sure you download the correct Windows 10 iso which corresponds with your current Windows 8.x version (Home, Pro, 32 or 64 bit).
John CarneyReliability Business Tools Analyst IIAuthor Commented:
Thanks to both of you. I feel pretty confident now that I won't have a problem restoring 8.1 if need be. Am I correct in assuming that my files, folders and registry, etc. won't be messed up if I do the restore?

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Tyler BrooksNetwork and Security ConsultantCommented:
No you shouldn't have any issues with it, I've done 2-3 restores now and have yet to encounter any problems. If you want to make 100% sure to cover yourself, use Backup and Restore to create a system image before you do the upgrade and store it on an external drive.

Good Luck!
Everything stays the same as it was before the upgrade if you do a restore. I have also done it and had no issues.
Lionel MMSmall Business IT ConsultantCommented:
also you can continue to delay the update; I have chosen the latest possible delay for more than two weeks now--comes up every 3 days or so to "update now" and I have been delaying it for another 3 days until I am ready to pull the trigger and update.
John CarneyReliability Business Tools Analyst IIAuthor Commented:
Thanks to all of you. I decided to go ahead with the upgrade and so far so good!

~ John
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