I came back to my computer after a few minutes to find a “blue screen of death”, displaying a screen for Bitlocker. I’ve never heard of it, and never (knowingly) installed it. I was prompted for a “recovery key” but my keyboard and mouse appeared to be locked. After a “hard boot” (unplug and plug in again) everything seemed to be OK.
I know now that it has something to do with encrypting files - but has it detected anything wrong with my system? Can I get rid of it if its messages will continue to pop up?
It’s a built-in feature of Windows since Vista. Open the Start menu and type “bitlocker” into the search box, then click on “Manage Bitlocker” which will open a Control Panel window, from which you can turn it off or otherwise manage it.
Bitlocker has been a standard part of Windows for many years now (since at least Windows 7 edit: Vista, as DCnDC pointed out). It is Microsoft’s name for the system software that encrypts your computer to safeguard your files from thieves, digital or physical.
The downside is that you must safeguard your recovery key, or you risk losing access to your own computer. You got lucky this time since it was in a not-fully-locked state where a restart still let you log back in (presumably with a username & password), but don’t count on that.
But why did it apparently try to run itself? I’d be worried that my computer has been hack since setting Bitlocker is a cheap and easy way to ransomware someone’s computer.
The system attempted to access the disk and for some reason could not, triggering the BSOD. Whatever it was, a hard reset fixed it, so it was probably just the system temporarily lost its TPM trust. OP can check their system logs (Event Viewer > Windows Logs > System) to see if there was a firmware or TPM event at that time.