Definition - What does Clean Boot mean?
Clean boot is the process of starting a computer system with only the most essential files and services required by the operating system. It is a leaner approach to booting a computer that requires that at least the startup services and device drivers be loaded.
Techopedia explains Clean Boot
Clean boot is primarily a troubleshooting technique used to identify and resolve performance issues within the booting process, including software conflicts, error messages and more. Typically in a clean boot the usual functionality, appearance, device support and other optional features might be restricted. This is done to help the system administrator diagnose and identify the problem within each component. When the issue is resolved, the computer can be rebooted again to restore all features and functionality to a normal operating environment.
In a Windows operating system, the system configuration utility (MSCONFIG) is used to select and initiate a clean boot process.