Revert To Startup layout automatically loads _startup.ui, which returns the user interface to its startup settings. This temporary system file is created automatically when you start 3ds Max. Use this option to return the UI to startup settings.
For information on how to load different UI schemes on startup, see Load Custom UI Scheme.
If the Preferences dialog 
General panel Save UI Configuration On Exit switch is on when you exit 3ds Max, the current UI file is overwritten.
