Partitions are divided areas on your built-in storage device. Dividing the built-in storage device into more than one partition may have various advantages, such as separating the system files from your data files.
Your VAIO computer has only one partition (C: drive) as the factory default setting.
If you want to store data in another partition, such as D: drive, change the partition size and create a new partition.
For more information on how to create partitions, see Creating Partitions.
Some models may have D: drive as the factory default setting.