You signed up for the Windows 10 upgrade, but now that the bits are ready, you're getting cold feet. I understand. But there's one little problem: Your Windows 7 or 8.1 machine won't install any updates until you install Windows 10. Windows Update may say, "Your upgrade to Windows 10 is ready," and if you check for updates, you get "Windows Update cannot currently check for updates, because you must first restart the computer so that a previous installation can be completed."
You may get a message that says, "Your upgrade is ready to install" and then, "Great, we'll get the upgrade started." I've seen hundreds of posts (and more than a few emails) from people stuck in the same boat. If you accepted the offer for Windows 10 and later decided that you aren't ready, Microsoft locks your machine into a situation where it's very difficult to say no.
I've been playing around with this problem for a couple of weeks, ran it through a dozen testers on AskWoody.com, and think that maybe -- maybe -- this approach may work. Please test it. The worst that'll happen is you'll end up in the same position, after 20 minutes to an hour of hassle, for which I apologize.
Step 1. Wait until you have a spare hour. This is good to do before you head out to a meeting, to lunch, or at the end of the workday.
Step 2. Turn off Automatic Update. Go into Windows Update (in Win7, using an administrator-level account, click Start, Control Panel, and then System and Security; in Win8.1, while looking at the old-fashioned Windows desktop, hold down the Windows key and press X, then choose Control Panel, System and Security). Under Windows Update, choose this setting: "Check for updates but let me choose whether to download or install them."
Step 3. Hide the upgrade, if you can. In Windows Update, click Show all Available Updates. If you see an entry for Upgrade to Windows 10 (many of you won't), right-click on Upgrade to Windows 10 and choose Hide Update.
Step 4. Delete the installation files. In File Explorer, right-click on your C drive and choose Disk Cleanup. When Explorer comes up for air, click the box marked Clean up System files. When the list appears, check the box marked Temporary Installation Files (it'll be big -- 5.8GB or so). Click OK. There's a message that says "Are you sure you want to permanently delete?" Click Delete Files. Wait ... and wait ... patiently. Remember, this is Windows.
Step 5. Get rid of the GWX (Get Windows X) patches. Back in Control Panel, Add or Remove programs, on the left click View installed updates. Look for KB 2952664 (likely on Win7 systems) and KB 2976978 (likely on Win 8.1). Also look for KB 3035583 (both Win7 and Win 8.1). If you find any of them (hint: click the column heading to sort alphabetically), click on it, and click Uninstall. (t/h EP)
Step 6. Reboot. Windows will prompt you to reboot. Do it. And wait. And wait. It may take an hour to reboot.
Step 7. Permanently disable the GWX patches. The minute you've rebooted, go back in to Windows Update and "hide" KB 2952664, KB 2976978, and/or KB 3035583. To hide them, run Search for Updates, right-click on the entry and choose Hide. (t/h CT)
Step 8. For good luck, reboot again. That probably isn't necessary, but it'll kill off any process that thinks it should be downloading the Windows 10 installation files.
On the systems I've tested, that'll remove the downloaded Windows 10 files, the obnoxious nags in the system tray, and the "Your upgrade to Windows 10 is ready" notification in Windows Update. I'm not absolutely sure it'll work in all cases, but the worst case is you've lost some time -- you aren't twiddling with any registry settings or doing anything that might cripple your Win7 or Win8.1 system. It's strictly a home remedy, but Microsoft certainly isn't going to distribute a magic fix.
Suggestions and in-the-wild status reports most welcome. Hit me in the comments.