How symptom scope and recent changes distinguish Windows boot, profile, application, service, and security problems.
Windows symptoms should be classified before repair. A failure limited to one application, one user profile, or one startup item is different from a boot-path failure or a security incident.
| Symptom | First diagnostic lane |
|---|---|
| Operating system is not found | Boot order, storage, partition, or recovery path |
| Sign-in works but the desktop is unstable | Startup item, profile, service, or recent update |
| One application crashes | Application dependency, compatibility, update, or user profile |
| Service will not start | Service state, dependency, permission, or recent change |
| Unexpected redirects, alerts, or pop-ups | Browser compromise or other security investigation |
When the symptom starts immediately after an update, driver, or application change, test a targeted rollback, uninstall, or isolation step before broad recovery.