Boot-time or offline defragmentation
Boot-time or offline defragmentation lets you defrag even the system files that are normally locked by Windows. Offline defrag runs on system startup, before the operating system loads, and allows you to streamline the following system files: MFT files, Paging file, Hibernation file and Windows Registry files. Defragmenting system files will make your Windows more responsive, speed up system loading and overall performance.