September 2026 Windows Update — Known Problems and Fixes

September's Windows update has been out for two days. Two things have surfaced already. One's a backup problem, the other's a support deadline that'll catch people out. Here's what's happening and what you should do.

File History backup has stopped working

File History is the backup tool built into Windows. It copies your documents, pictures and desktop files to an external drive on a schedule, so if the laptop dies or you delete something by accident, you can get it back. Since the September updates went on, including KB5124008, a lot of people are finding it simply doesn't run any more.

What they're describing is consistent. The File History panel opens, then throws an error even though the external drive is plugged in and working. The "Last Backup" time sits frozen on a date from days or weeks ago. Nothing new gets copied. There's no crash and no warning box, so unless you go and look, you'd never know.

This one predates September, to be fair. The reports go back to earlier 2026 updates and people had hoped the September cumulative would put it right. It hasn't. KB5124008 goes on and File History stays broken.

Who's affected: people on Windows 10 or Windows 11 who set File History up and rely on it. That's a smaller group than it sounds. File History doesn't switch itself on. Somebody has to plug in an external hard drive and configure it through Control Panel, which most home users have never done. If that's never been you, this isn't your problem and you can skip to the next section.

If it is you, and it's been backing up quietly in the background for months, go and check it. That's the trouble with a silent failure. The backup you're counting on may have stopped in March and you wouldn't have noticed until the day you needed it.

How to check if File History is still working

Two minutes, and you'll want your external drive plugged in first.

1. Press the Windows key on your keyboard. It's the key with the four-part flag symbol, usually bottom-left next to the space bar.
2. Type Control Panel and press Enter. The Control Panel window opens.
3. Click System and Security.
4. Click File History.
5. Look at the line that says Last copied files on: followed by a date and time. If that date is recent, you're fine. If it's weeks or months old, or the page is showing an error message instead, File History has stopped running.

No File History option under System and Security? Then it was never set up on this PC, and none of this affects you.

One thing to try while waiting for a fix

People on the Microsoft Community Hub threads are reporting that reselecting the same drive gets it going again. Microsoft hasn't confirmed this and it's not an official fix, so I'd treat it as worth a go rather than a guarantee. It takes a minute and it can't do any harm.

1. Make sure your external drive is plugged in and Windows can see it.
2. Press the Windows key, type Control Panel and press Enter.
3. Click System and Security, then File History.
4. In the menu down the left-hand side, click Select drive.
5. Click your external drive in the list. It'll be the same one that's already selected. Click it anyway.
6. Click OK.
7. Back on the main File History page, click Run now if you can see it, then wait a few minutes and check whether the "Last copied files on" date has updated to today.

No official fix yet, and Microsoft hasn't publicly acknowledged the problem at all. If File History is how you back up your files and this is affecting you, get in touch.

Windows 11 24H2 stops getting updates on 13 October

Not a bug, this one. A deadline, and it's the sort that goes unnoticed until it's passed.

Windows 11 comes in versions, and 24H2 is one of them. It's not the same thing as Windows 11 itself. Microsoft puts out a new version roughly once a year and supports each one for a fixed stretch, and 24H2's stretch runs out on 13 October 2026. That's 33 days from now. The current version, 25H2, carries on being supported as normal, so this only bites if your PC is still sat on 24H2.

Home and Pro editions are the ones losing support. Enterprise and Education get until October 2027, which is no help to anyone reading this at a kitchen table.

After the 13th, a machine on 24H2 gets no more security patches, no bug fixes, and no time zone updates. The security patches are the part that matters. Criminals watch for versions of Windows that have gone out of support, because every hole found after that date stays open permanently. It's the same reason I've been nagging people off Windows 10 all year.

How to check which version you're on

1. Hold down the Windows key and press the letter I. The Settings window opens.
2. In the list down the left-hand side, click System.
3. Scroll to the bottom of that page and click About.
4. Under the heading Windows specifications, look at the line marked Version. It'll say 24H2, 25H2 or something older.

If it says 25H2, you're already sorted and you can stop reading this section. If it says 24H2, carry on.

How to upgrade to 25H2

It's free, and it's an ordinary Windows update rather than a reinstall. Your files, programs, settings and desktop all stay exactly where they are. Budget 20 to 30 minutes and don't start it ten minutes before you need the laptop.

1. Hold the Windows key and press I to open Settings.
2. Click Windows Update at the bottom of the left-hand list.
3. Click Check for updates.
4. Windows 11, version 25H2 should appear as an available update. Click Download and install.
5. Leave it alone until it asks you to restart, then restart. It'll spend a while on a screen telling you not to turn the PC off. Believe it.

I won't dress this up as an emergency, because it isn't one today. Nothing breaks on 14 October and the PC will keep working. But there are only 33 days in it, and October is exactly the sort of month where a thing like this gets forgotten. Do it this week and stop thinking about it.

Should you still install the update?

Yes. No hesitation on this one.

September's update fixes somewhere between 966 and 974 vulnerabilities, the largest single patch Microsoft has ever shipped, and two of them were already being used to break into machines before the update came out. CVE-2026-81963 and CVE-2026-85880, both privilege escalation flaws rated 7.8. That means an attacker who's got a small foothold on your PC can turn it into total control of the machine. Those are real, in the wild, right now.

Neither of the problems on this page comes anywhere near justifying skipping that. The 24H2 deadline is a reason to update more, not less. And the File History bug was already there before September, so holding off on the update wouldn't have spared you it.

One caveat if File History is your only backup: install the update, then run the check above and make sure it's still copying. If it isn't, try the drive reselection, and copy your important folders across by hand until it's fixed properly.

If something's gone wrong since you installed September's update and you'd rather someone just looked at it, local computer repair is here for the things that need sorting in person.

Mark

Mark has been fixing computers since the late '90s and went self-employed in 2008. Based in St Helens since 2013, he works evenings and weekends from his home in Laffak — friendly, affordable repairs for PCs, laptops, and Macs. See reviews on Google