Reset Windows Password: View hidden partitions
Most modern Windows systems require at least one hidden partition for successful functioning. These invisible to users partitions are used by OS during startup, recovery or system update. Furthermore, some advanced users can create their own hidden partitions to prevent others from viewing and accessing private files and personal information.

The Volume Explorer tool can mount hidden partitions temporarily and use them as regular logical drives. To attach a hidden partition, select it from the list of found volumes and click the 'Mount selected volume' button.

Don't forget to detach it if you no longer need it.
Do know that some partitions may be unusable even after a successful mounting. For example, the partition has a raw file system, some encryption software protects it and so on.