Its support is controlled with a REG_DWORD value named `VolatileBoot` inside the registry key `HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\Configuration Manager` . Its implementation is very trivial: when enabled, CmpShareSystemHives is set to TRUE and doesn't change state during runtime. In a sense this is similar to what happens in WinPE-boot, except that ALL hives without exception (system hives and others) will be loaded in shared mode.