Windows systems often use more than one mass storage device (MSD) driver. However, only one of them is associated with the boot partition of the drive where Windows is installed.
By default, BMR loads all MSD drivers during the boot phase of the restore. You can edit the configuration so that only the driver that is associated with the boot partition is loaded. Do so if the loading all of the MSD drivers interferes with the boot process of the restore.
The system drive is always mapped and cannot be moved. However, you can resize it if you map disks before the restore.