If sign-in succeeds and the screen then becomes blank, the fault may differ from a boot failure. Note whether the pointer or Task Manager 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
Whether Task Manager opens, external display state, recent graphics changes, and Windows build.
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
Protect access to files if possible, inspect recent display-driver changes through the official PC maker, and use Safe Mode if Windows is otherwise inaccessible.
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
Do not make registry or shell changes from unverified downloads.
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.