A stop error after an update does not prove the update itself is defective. Record the stop code and update history, then check whether Windows can still boot.
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
Exact stop code, KB number, installation time, and whether Safe Mode starts.
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
If Windows starts, save files and check update history. Disconnect recently added peripherals. If the crash repeats, compare the stop code with the code catalog and check the current release-health page.
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
Repeated startup failures or an inaccessible drive require a backup and recovery-key check before recovery changes.
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.