Why Windows Isn’t Booting After A Power Outage – 8 Easy Fixes

PCs work well… most of the time. However in rare cases, Windows computers can have major problems after a power outage – even resulting in the PC failing to boot up. This is because modern PCs are actually quite complicated: a range of PC hardware, BIOS options and operating system layers all have to work well together for a PC to successfully start up.

However an unexpected blackout can corrupt any number of these areas, leading you to think that your entire PC hardware has been fried. Luckily there’s often a number of simple fixes to this problem.

How To Get Windows Booting Again (After An Outage)

How To Get Windows Booting Again After A Power Outage

There can be a number of different areas to check and/or fix after a power outage: from the physical power plug, to Windows settings. However I will start discussing the most common fixes first.

Fix #1: Remove All Power Sources (Cords & CMOS Battery)

Your computer’s motherboard or PSU might be in a weird state after an unexpected blackout, and so if your PC isn’t booting, the first thing I usually do is remove the power plug and also flip the PSU switch to off:

The power plug and switch at the back of my desktop PC
The power plug and switch at the back of my desktop PC

I would then wait a few minutes, before plugging the PC back in and flipping the switch on again. Then try powering on and see if your PC boots again. Hopefully it now works, but if not, I would also look to remove the motherboard’s CMOS battery.

Tech Tip: The CMOS battery is a physical coin battery that sits in your BIOS and helps it to retain all its settings and firmware. As a result, the CMOS battery can be crucial for helping your PC boot up properly.

To remove the CMOS battery, open up your PC case and locate the CMOS battery (it will be the only coin battery in your motherboard):

Two M.2 NVMe drives installed in an Asus B550 Plus motherboard
The CMOS battery can be seen towards the top left of this picture.

Pry it out with a flat edge screwdriver and wait at least 5 minutes, and then re-insert the CMOS battery. Try booting up your computer again. Hopefully flushing out all your motherboard’s boot settings will prompt your computer to start up again.

Fix #2: Enter Windows Recovery Mode

If your computer does already POST (i.e. boot up and show the motherboard screen) but it’s then really buggy when loading into Windows, it’s possible that Windows has become corrupted due to the brownout or blackout you experienced.

Windows has a built-in recovery environment (RE) that can help you here, because it has a number of checks and repair options that it can perform.

The way that you enter Windows RE can vary, however if you are able to boot into Windows, try going to the Control Panel, then Update & Security and finally “Recovery”. Click “Restart Now” under advanced start-up to boot into the recovery mode:

One way of entering into the Windows recovery environment
One way of entering into the Windows recovery environment

However if you can’t even login to Windows, you should instead try turning the computer off and on 3-4 times once you see the Windows screen. In other words, hold down the case’s power button when you see any Windows logo, then boot up again, and repeat this process 3-4 times.

Eventually this will force Windows to boot into the recovery environment. Once you’re here, there are a number of checks you can carry out – however I would firstly go to “Advanced Options” then UEFI Firmware Settings and verify that the Windows install/startup disk is correct.

If the startup disk looks to be the correct system disk (for example, you have installed Windows on your NVMe SSD and this is clearly listed), you should move onto an automatic repair.

To do this, click the “Automatic Repair” option, also within the Advanced Options. This should run through fine, but if it says it failed, the below YouTube video explains how to fix the dreaded ‘automatic repair loop’:

Fix #3: Check Your BIOS Boot Options

If your computer is booting up but not quite reaching your OS, you should also double check the boot options look correct within the BIOS. To do this, enter your BIOS in the usual way (which often involves restarting and pressing DEL, F2 or F12 – but some motherboards use a different key).

Then head over to the boot options, and you should see something like this:

Looking at the available boot options in my Asus BIOS
Looking at the available boot options in my Asus BIOS

If you have multiple drives in your PC, you will have installed Windows on a specific drive. So double check that the right drive is listed here (otherwise your motherboard will keep booting into the wrong thing).

If you only have a single hard drive/SSD installed, but you see multiple options here, check if you have any USBs or DVDs inserted in your computer. These can sometimes confuse a BIOS – especially after a power outage – causing the motherboard to try and boot into these instead.

Temporarily remove the USB/DVD and boot into your BIOS again, checking that the boot option(s) now look correct.

Fix #4: Reset Your BIOS To Default Settings

If nothing has worked up until now, it’s possible that some previously changed BIOS settings (including any overclocking) might be stopping your PC from properly booting. In this case it’s usually best just to start your BIOS again with the original defaults.

To do this, boot into your BIOS as described earlier, and look for an option like “Restore factory defaults” or “Load Optimized Defaults”. The exact wording (and location) will vary, so you might need to check your motherboard’s manual, but it’s worth resetting your BIOS’ settings:

The option to restore my BIOS to default options
The option to restore my BIOS to default options

Once this is completed, restart your PC and hopefully you can now boot into Windows successfully. If you still have trouble, though, you should open your PC and remove the CMOS battery for 5 minutes (as I explained earlier):

Two M.2 NVMe SSDs of 2280 size installed in an Asus motherboard
The CMOS battery is just above my M.2 drive (to the left of the CPU cooler bracket)

This method will also reset your BIOS to its factory defaults, hopefully meaning that you can then boot into Windows without any errant BIOS settings confusing things.

Fix #5: Try Changing The PSU And Power Cord

A power outage or surge might have caused damage to your PSU or the power cord running to it – this is probably the most common physical reason why a PC won’t boot up after an outage.

If you have a spare power cord lying around, try this out first and see if your computer starts booting up again. But if it doesn’t, you might unfortunately need to order a brand new PSU:

The Corsair RM 750x PSU with various cables connectors in the background
A new Corsair RM 750x PSU.

Unfortunately swapping out the PSU isn’t always easy because you will need to change all the individual PSU cables running to each component, and also re-do any cable management you had. But this might be a necessary step if your PC is refusing to even boot after an outage.

Fix #6: Could Your PC Hardware Be Damaged?

Following on from the point above, one of your other pieces of hardware might have become damaged in the blackout. For example, if the case fans spin but your motherboard LEDs don’t come on, your motherboard itself might be damaged.

Alternatively if your system POSTs but then the motherboard complains that there is no operating system installed, it’s possible that your drive has become corrupted and lost some critical system files.

Unfortunately there’s no simple way of figuring out which specific piece of hardware might be damaged – it’s just a case of debugging any obvious causes, and then restoring to trial and error. Remember, though, that stripping your PC back to its base hardware can be a good idea:

A work in progress desk build booting up fine containing a Ryzen 5 CPU Gigabyte AB350M motherboard and Corsair CX550M PSU
Checking that a basic motherboard, CPU and RAM set-up starts as expected.

This will allow you to clearly see if all the key parts of your system run as expected. If it does, you can then plug in a display cable and check whether any display appears on the screen (for example).

Fix #7: Run Various Health Scans

The next step for diagnosing your PC’s no-boot issues is to run various health scans. If you can boot up into Windows, then you will be able to check your RAM with Windows Memory Diagnostic and verify your drive’s health with SMART checks.

The easiest way to run a drive SMART check is by downloading CrystalDiskInfo, however you can also check your drives by opening Command Prompt and typing wmic diskdrive get status. After a few minutes of waiting, it will hopefully reply “OK” for each of your drives.

However if you can’t boot into Windows, fear not – you can download various health-check tools to a USB, and then boot into the USB. You can often specify to boot into the USB within your BIOS – just make sure that your USB is plugged in when you restart your PC.

For example, you can download MemTest86 onto a USB. Just be sure to make this a bootable USB first – you will need access to a separate computer in order to do this. The video below shows how to do this:

If any of these health checks highlight an issue, you might need to replace the relevant component – i.e. buy new RAM if MemTest86 highlights corrupted memory segments.

Fix #8: Consider Reinstalling Drivers… Or Even Windows!

As a final point, if you are usually able to boot into Windows – but you’re getting loads of weird behavior (such as programs crashing or the screen going blank) – you might want to consider reinstalling drivers, or potentially resetting Windows.

Sometimes this can just be as simple as using the Windows uninstall tool to remove a driver, and then installing it again (by downloading the latest version from the manufacturer’s website).

However you can also use Windows’ built-in recovery tools, for example you can use the “Reset this PC” option under the “Recovery” section of control panel – which will keep your personal files, but delete everything else:

The recovery options for Windows 10 under the control panel
The recovery options for Windows 10 under the control panel

Once this process is complete, you will need to reinstall any programs and drivers that you need. But this can be a great way of fixing problems with your Windows install, without doing a full-blown reinstall.

Future Tip: Get Surge Protectors And A UPS

A UPS running on backup battery power
A UPS running on backup battery power

If you’re reading this article after suffering PC problems from a blackout, you might already be thinking this – but I wanted to re-iterate a key point.

You should always have your computer plugged into a surge protector plug, and ideally also run it through a consumer-grade UPS. These will help ensure that your computer won’t suffer damage from an unexpected power outage in the future.

While UPS’ aren’t exactly cheap (they are usually a few hundred dollars at least), they can be a critical purchase because they will allow your PC to gracefully shut down when an outage is discovered.

Windows doesn’t have standard graceful shutdown features built into it, however this article discusses how you can still pair your Windows PC with a UPS to massively save energy usage during a blackout – hopefully protecting your hardware and OS from taking damage.

cropped A picture of me Tristan
About Tristan Perry

Tristan has been interested in computer hardware and software since he was 10 years old. He has built loads of computers over the years, along with installing, modifying and writing software (he's a backend software developer 'by trade').

Tristan also has an academic background in technology (in Math and Computer Science), so he enjoys drilling into the deeper aspects of technology.

Tristan is also an avid PC gamer, with FFX and Rocket League being his favorite games.

If you have any questions, feedback or suggestions about this article, please leave a comment below. Please note that all comments go into a moderation queue (to prevent blog spam). Your comment will be manually reviewed and approved by Tristan in less than a week. Thanks!

10 thoughts on “Why Windows Isn’t Booting After A Power Outage – 8 Easy Fixes”

  1. Hi…my #1 computer (11 years old now) totally crashed last December immediately after a Windows Update. But it eventually worked again a while later. It cannot see any of the drives except the C drive, an SSD with Windows on it. I am intending to build a new computer anyway…but it is serious when a Windows Update can do this. My #2 computer is working fine…

    • Hi Jeffrey, that sucks for sure. It’s definitely concerning that a Windows Update caused that. It sounds like some weird data corruption if it can’t see the other drives, but hopefully a Windows reinstall (or new PC build) will naturally fix that issue.

    • Exactly the same thing happened to me. Note that even my DVD stopped working altogether. ie: it would not even eject. W10 22H2 was the culprit, I switched to an SSD and preformed a fresh install to fully recover. Note that the mechanical HDD was not at fault, it has simply become too slow for W10 as of 22H2.

      • Huh that’s concerning for sure. Sorry to hear it – but thanks for sharing your experience. I guess that reasoning does (sort of) make sense, especially if the HDD was starting to have degraded performance.

  2. My humble Acer Aspire has started generating the “Operating System Not Found” after power outages since I switched to an SSD (because of W10 22H2). However, I can easily recover with the (F12) boot menu. It reads;

    Boot Menu
    1. Windows Boot Manager
    2. HDD:
    3. ATAPI CD/DVD:

    Option 2 works every time; like nothing ever happened. Therefore, a power outage simply causes a corruption of the Windows Boot Manager (UEFI architecture). In other words, its a bypassable, Microsoft problem. My older Compaq (BIOS era) appears to be immune to this issue.

  3. I have also been getting “Operating System Not Found” messages after power outages since upgrading my laptop to an SSD because of Win 10 22H2. I can pretty much reproduce the failure on demand. I can confirm the issue is with the Windows Boot Manager, since my OS and data partitions remain intact. More to the point, I use the HDD option of my laptop’s F12 boot menu to recover. Furthermore, the Windows Boot Manager repairs itself on the following restart.

    • Thanks for the follow-up comment, it’s good that WBM manages to repair itself – phew! I always find the self-repair feature a bit temperamental, but it’s great that it has worked out for you.

  4. It turns out that Microsoft introduced the issue many many months ago while trying to address a Secure Boot vulnerability exploited by BlackLotus UEFI malware. I am pleased to report, as of this week, that a power loss no longer results in the “Operating System Not Found” message on my Acer Aspire. I rest my case.


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