Like its predecessors, Windows 7 automatically defragments system files every time you start your computer. If you defragment your hard drive regularly, you can disable this feature you will save time you turn on your PC.
Go to the registry:
Type Regedit in the search bar Windows
Search key: HKEY_LOCAL_MACHINE \ SOFTWARE \ Microsoft \ Dfrg \ BootOptimizeFunction (create it if it's not there)
Set the value chain and it put the value N (Right Click> New> String Value)