A black display before sign-in needs a display-versus-boot check. Do not assume it is a blue-screen stop error unless a stop code appears.
Protect your files first
Back up important files when possible. If the drive is encrypted, locate the BitLocker recovery key before recovery changes. Stop if storage appears to be failing or this is a work or school managed PC.
What to record
Maker logo, backlight, cursor, external display, and Windows startup sound.
The exact message, Windows version, and whether the desktop still opens matter more than a guess based on the symptom name.
Try these safer checks
Verify power and display inputs, remove an external monitor ambiguity, and note whether Windows RE can be reached.
Change one thing at a time. After each check, see whether the same symptom returns and write down what changed.
When to stop and get help
If there is no display even in firmware, contact the PC maker for model-specific diagnostics.
If this is a work or school device, contact its administrator before changing managed settings.
Keep track of your checks
This checklist stays in this browser session. It is not sent to WinErrors.