Unexpected weird issues on boot up

[ne0]

Logged in to my PC today and had a few unexpected things happen. Never had any issues like this before so looking for some theories/advice as to what might be going on...

1. Splash screen with bios prompt appeared (press X to enter BIOS, etc) - usually I would go straight to windows sign in screen so this was unusual.
2. I enter the BIOS and start having a look around - noticed XMP was disabled. I could swear I had this enabled but always a chance I disabled it at some point so I enabled it and saved.
3. Get to the Windows sign in screen and I get a message telling me my PIN is unavailable. I have no other way of signing in.
4. Had a Google on my phone and a couple of things caught my attention - TPM or PTT settings to do with security.
5. Went back into the BIOS and reset everything to default. Went to save the settings and on the changes summary, sure enough I saw PTT (TPM) setting Disabled > Enabled.
6. Enabled it and sure enough I was then able to sign in to Windows.

How did the PTT/TPM setting get switched off (I haven't been in the BIOS for months...)?
If the PTT/TPM setting was always disabled then why didn't I have any issues signing in before and besides if it's enabled by default then something must have disabled it?

I also noticed that the system date was correct but the time was out by a few hours...

All very strange. Do motherboards still have CMOS batteries? Is something wrong with my motherboard? Do I have security issues? Any advice hugely appreciated, cheers.

 

[Tetras]

Do motherboards still have CMOS batteries?

Yes.

The most likely conclusion I'd come to is that it was reset for some reason and returned to defaults (to ensure you can boot).

A battery on the way out is a possibility.

It could also be due to instability.

Are you overclocking? How fast is your memory?

Have you changed anything recently? E.g. memory upgrade, new USB devices?

 

[ne0]

Yes.

The most likely conclusion I'd come to is that it was reset for some reason and returned to defaults (to ensure you can boot).

A battery on the way out is a possibility.

It could also be due to instability.

Are you overclocking? How fast is your memory?

Have you changed anything recently? E.g. memory upgrade, new USB devices?

Not all of the settings were changed so the BIOS hadn't actually returned to default settings. When I reset the BIOS to default I could see that some of my custom settings were still set which is strange. Why would XMP and TPM settings in particular have been changed? So strange.

Not overclocking at all. In fact the only thing you could consider an overclock would be XMP and the BIOS said that was disabled for some reason (even though I'm sure I had enabled it).

No instability at all recently, this is completely out of the blue.

Haven't changed any components at all and everything's been running well for months.

The last bout of instability I had was when Nvidia released the 50 series and I had major issues with system reboots due to their drivers but that eventually stopped after a few updates.

RE. the CMOS battery - that's the first thing that sprang to mind and I've had to replace once many moons back in a much older rig, but not sure if what I'm seeing is a symptom of that.

 

[JollyJamma]

Did you let someone else use your computer or do you have a kid who likes to mess around with stuff?

I used to mess around with my parents computer so much that they bought me my own one when I was 15.

 

[sastusbulbas]

It usually takes a long time of inactivity to render a CMOS 2032 battery dead, on one of my old PC's which I recently put on, the battery was dead, I lost all BIOS settings for overclocking the CPU, memory was down to default non XMP settings, fan profiles gone, time was off too, Windows 10 booted into repair mode.

This PC had sat unused for a couple of years though, and was an ancient LGA 775 system.