My wife's laptop is a Dell Inspiron 7353 2-in-1, purchased in 2016, with
Windows 10 Home, factory installed, with an SSD. All has been running
fine for many years. She leaves it plugged in and running 24/7.

Yesterday, she was using it and stepped away for a few minutes. When she
came back, the screen was black. She pressed the enter key, and the
keyboard lit up, but the screen remained black. She pressed the power
button, and the machine showed "No boot device found". She pressed the
power button again, and up came the same message. Round and round she
went.

I powered up and F12'd into the boot menu, and it showed it was set to
Legacy. Hmmm...that's not a factory install. I changed to UEFI, and the
machine booted up just fine.

I powered off and back on, and got "No boot device found".

I checked the BIOS settings, and sure enough, boot was set to Legacy, and
Secure boot was disabled. Legacy Option ROMs was enabled.

How in the world did the boot change from UEFI to Legacy? I'm not aware
of any human intervention. Very strange.

Boris <Boris@invalid.invalid> wrote in
news:XnsB0CA6E12EB8ACBorisinvalidinvalid@135.181.20.170:

> My wife's laptop is a Dell Inspiron 7353 2-in-1, purchased in 2016,
> with Windows 10 Home, factory installed, with an SSD. All has been
> running fine for many years. She leaves it plugged in and running
> 24/7.
>
> Yesterday, she was using it and stepped away for a few minutes. When
> she came back, the screen was black. She pressed the enter key, and
> the keyboard lit up, but the screen remained black. She pressed the
> power button, and the machine showed "No boot device found". She
> pressed the power button again, and up came the same message. Round
> and round she went.
>
> I powered up and F12'd into the boot y-menu, and it showed it was set
> to Legacy. Hmmm...that's not a factory install. I changed to UEFI,
> and the machine booted up just fine.
>
> I powered off and back on, and got "No boot device found".
>
> I checked the BIOS settings, and sure enough, boot was set to Legacy,
> and Secure boot was disabled. Legacy Option ROMs was enabled.
>
> How in the world did the boot change from UEFI to Legacy? I'm not
> aware of any human intervention. Very strange.

I forgot to mention that the first time my wife pressed the power off
button, Dell's Support Assist came up and said it was doing a hardware
check. It came back with hardware ok, and then black screened followed
by the "No boot device found" merry-go-round.

On 11/28/2023 1:59 PM, Boris wrote:
> Boris <Boris@invalid.invalid> wrote in
> news:XnsB0CA6E12EB8ACBorisinvalidinvalid@135.181.20.170:
>
>> My wife's laptop is a Dell Inspiron 7353 2-in-1, purchased in 2016,
>> with Windows 10 Home, factory installed, with an SSD. All has been
>> running fine for many years. She leaves it plugged in and running
>> 24/7.
>>
>> Yesterday, she was using it and stepped away for a few minutes. When
>> she came back, the screen was black. She pressed the enter key, and
>> the keyboard lit up, but the screen remained black. She pressed the
>> power button, and the machine showed "No boot device found". She
>> pressed the power button again, and up came the same message. Round
>> and round she went.
>>
>> I powered up and F12'd into the boot y-menu, and it showed it was set
>> to Legacy. Hmmm...that's not a factory install. I changed to UEFI,
>> and the machine booted up just fine.
>>
>> I powered off and back on, and got "No boot device found".
>>
>> I checked the BIOS settings, and sure enough, boot was set to Legacy,
>> and Secure boot was disabled. Legacy Option ROMs was enabled.
>>
>> How in the world did the boot change from UEFI to Legacy? I'm not
>> aware of any human intervention. Very strange.
>
> I forgot to mention that the first time my wife pressed the power off
> button, Dell's Support Assist came up and said it was doing a hardware
> check. It came back with hardware ok, and then black screened followed
> by the "No boot device found" merry-go-round.
>

"She leaves it plugged in and running 24/7."

And the laptop main battery is removed ?

What could have happened, is the CR2032 battery is flat, and
the BIOS has no power for the Southbridge RTC RAM that holds a few of the settings.

But, it would take complete power loss, to reset the settings.
And that is missing from the story. The soft power button would not work
on the thing, unless there was a supervisor voltage present and the
supervisor voltage can also provide BIOS power.

The shelf life of a CR2032 is ten years. The small coin cell, the state of
it is not assured after ten years. The CR2032 battery can drain in a bit less
than three years, if a computer has no power whatsoever (is left in the
junk room). The CR2032 battery lasts longer, if the PC always has power.

Some computers use an LR2032 instead of a CR2032, and those are rechargeable
coin cells. The failure characteristics are different, if a product uses
an LD2032. Eventually an LR2032 will completely fail as well, and
will no longer accept a charge. And this can cause the BIOS settings
to get reset.

I don't think this is a particular good match for your description,
but it's about all I've got as an answer.

Paul