shuts down just about everything that isn't absolutely necessary to get Windows to launch. What is left running, is running with the most stable drivers available and any accelerators or “tweaks” are turned off too. Like video and other hardware acceleration.
This is designed to be as close as can be to a stable environment.
It is slow and clunky, but it shouldn't crash.
It also disables 3rd party addons.
While there are a variety of issues you can use this for Safe Mode is mostly for hardware issues or issues where a software package left regular Windows inaccessible.
does not care about the windows environment. It assumes that Windows is not the problem and that it works fine.
It removes 3rd party vendor addons that are loaded on start up.
While there are a variety of issues you can use this for the purpose of Clean Boot is mainly to troubleshoot software compatibility issues.