System reserved partitions are used to store vital operating system files, such as boot data, the boot loader and the startup files used for BitLocker drive encryption.
System reserved partitions are used to store vital operating system files, such as boot data, the boot loader and the startup files used for BitLocker drive encryption. The System Reserved partition consumes 100 MB of space on Windows 7 and 350 MB of space on Windows 8 or Windows 10.
When Windows starts up, it reads boot loader off the System Reserved partition, and it boots Windows from the system drive.
For hard drives encrypted with BitLocker drive encryption, the System Reserved partition contains the necessary files for starting Windows.