A decade old PC, years of Windows 11 startup crashes, and the 1 pound part that fixed everything

[CosmicRay65]

Posting this partly as a confession and partly as a public service, because if it saves one person the journey I went on it was worth typing. My PC is over a decade old and ever since I upgraded it to Windows 11 it crashed regularly on startup. Some days it would get a quarter of the loading circle on the Windows logo, other days just a black screen of death, and then the daily ritual of Windows attempting recovery only to crash again at setting up repair

I tried everything, and I mean everything. BIOS update, cleaned the whole machine inside and out, swapped the old HDD for a new SSD, added more RAM, added more fans in case it was thermal, full Windows reinstall, system restore, the lot. Every fix bought a little hope and none of it stopped the crashes, and at times it was genuinely painful, you start doubting the whole machine

The culprit, in the end, was the CMOS battery. A part that costs about one pound, in a PC I have owned for ten years. The cruel twist is I had a couple of spare batteries in the drawer and tried those too, and it turns out they were ALSO dead, which is exactly what threw me off the scent for so long and then finally told me what the problem was

The working battery that solved it came out of a clicker I use for taking pictures on holiday, of all places. Dropped it in, and no crashes since, no more daily recovery attempts, no quarter circle of doom, just a boring ordinary boot every single time. Pictures of the patient and the tiny hero attached below

So the lesson for the thread, when you have ruled out the software side and it is not Windows update related, and you have ruled out the normal hardware suspects, check the stupid cheap thing before you spend another penny. I now have a new battery, a working PC, and a fortune saved on the replacement machine I very nearly bought. Anyone else been defeated for months by a part that costs less than a coffee?

[Myles95]

The dead spares are the killer detail, you did the right test and the test lied to you. That is the kind of luck that adds months to any diagnosis

[Grim Tracey]

Classic CMOS gotcha, when it dies the board forgets its settings every power off, and if it had anything non default saved, boot order, memory profile, the whole startup goes haywire. The pound coin battery takes down the thousand pound machine

[Leah_68]

Genuine question, did you not notice the clock resetting or BIOS settings going back to default? That is usually the tell tale before the crashes start

[SlowSocket]

Not always, if the machine stays plugged in at the wall the battery can be half dead for ages and only fully show itself in weird intermittent ways. The sneaky failures are the half dead ones

[RayOfLight32]

The battery from the holiday clicker is the best part of this story, somewhere a little camera remote made the ultimate sacrifice for the greater good

[SpinState52]

Been there with a different cheap villain, weeks of blue screens that turned out to be one SATA cable that had gone bad. The cheap parts fail quietly and let the expensive ones take the blame

[Georgia67]

In fairness the journey was not wasted, you came out the other side with an SSD, more RAM and better cooling, the crash was accidentally a full upgrade programme

[VoidRanger40]

This should honestly be a sticky, CMOS battery is step one on any machine past five or six years old and almost nobody checks it because it seems too small to matter

[QubitZero]

I would not make it step one myself, a dying battery causing full startup crashes rather than just settings amnesia is the less common version. Worth checking early because it costs a pound and a minute, but it is not the usual suspect

[Evan0]

That is exactly why it costs people months though, everyone including the internet tells you it only resets the clock, so it never gets tried until desperation sets in

[Holly]

Looking forward to the pictures, there is something properly satisfying about a photo of a ten year old tower back from the dead next to the coin sized part that nearly killed it

[CosmicRay65]

Posting because I had no problems until today when I unplugged my HDD which is idle except as a backup. I got the error again.

[Anchor99]

This is a good reminder that intermittent hardware faults can look like software problems for years. Windows crashing during startup naturally makes you suspect drivers, updates, corrupted system files or the Windows installation itself, especially when the machine eventually boots normally.

A flaky SATA cable or connector can produce exactly the sort of nonsense that wastes hours. The drive may work perfectly most of the time, then briefly lose communication during boot and leave Windows looking guilty for something that happened underneath it.

The useful lesson is to change one physical thing at a time and test properly after each change. Reseating the drive, trying another SATA port and replacing the cable are all cheap checks compared with reinstalling Windows or buying a new SSD.

And the fact that unplugging the old HDD brought the error back is particularly interesting. That suggests the drive or its connection may still be part of the boot chain, even if you think of it as merely a backup disk. Old PCs have a habit of accumulating dependencies nobody remembers creating.

[James93]

The HDD comment would have sent me straight into the BIOS. If the PC behaves differently depending on whether that drive is connected, I would want to know exactly what the firmware thinks the boot devices are.

Older systems can have confusing boot entries, especially after multiple Windows installations or drive replacements. You can end up with several boot options that look almost identical, and the machine may quietly choose one that depends on hardware you thought was obsolete.

Before changing anything, take photographs of the current BIOS boot settings. That gives you a reference if something goes wrong. Then check whether the intended system drive is actually first in the boot order and whether its bootloader is present.

It is amazing how often a "Windows problem" turns out to be a machine that has been booting through some weird historical arrangement for years. Computers do not complain about this while everything works, so the first clue often arrives when somebody unplugs an old drive.

[NicholasCleverley]

A decade-old Windows installation can accumulate some spectacular historical baggage. Different drives get added, Windows gets upgraded, partitions move around, boot settings change, and eventually nobody remembers why the machine needs something that appears unrelated.

The classic example is a PC with Windows installed on an SSD but the boot partition created on an older HDD. It works for years because both drives are always present. Then someone disconnects the HDD and suddenly the computer refuses to boot.

That does not necessarily mean the HDD is faulty. It can simply mean the computer has been relying on it for part of the startup process. Checking the partition layout before deleting or formatting anything is therefore really important.

If the £1 part fixed the crashes but the HDD still has this strange dependency, I would treat those as separate jobs. Fix the immediate fault, then tidy the boot arrangement once the system is backed up. No need to create a second problem while celebrating the first.