Article ID : S700023644 / Last Modified : 07/12/2018

My Computer shows less hard disk capacity than expected

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This article explains why the size of a hard disk as quoted by the Operating System will typically appear to be smaller than the size listed in the computer's specifications.

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Very Easy
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Any capacity difference observed is due to the following factors:

  1. Measurement differences

    Hard disk drive manufacturers quote the storage capacity in decimal units, such as 1 Terabyte (abbreviated 1TB). Tera means trillion, which gives the drive a capacity of 10^12 or 1,000,000,000,000 bytes.

    Operating Systems such as Microsoft Windows use the binary system instead, but still use the scientific, decimal terms to describe magnitude. According to the Operating System, 1 Terabyte (abbreviated 1TB) is equal to 2^40 or 1,099,511,627,776 bytes.

    The binary storage capacity reported by the operating system will typically be about 10% less than the decimal capacity stated in the specifications.

  2. Hidden partitions

    Depending on when your VAIO computer was produced and which operating system is installed on it, one or two hidden partitions are supposed to be on the hard disk drive:

    1. VAIO Recovery Partition
      This allows you to restore your VAIO computer to factory shipping state and typically takes up between 5 and 15 GB of disk space. If you want to remove this partition, you need to burn Recovery Disks and then use those to recover the VAIO back to factory state. When doing this to can choose to not create a Recovery Partition. For details, please refer to the Recovery Guide which is part of the documentation of your VAIO.

    2. System Reserved
      Windows 7 automatically creates a hidden partition with a size of 100 MB to store the Windows boot loader and  BitLocker information if needed. Please do not remove this partition.

    By consulting Disk Management (Start - Run - Diskmgmt.msc) you can see more details about the disks and volumes in your VAIO computer.