Secondary Hard Drive

• A secondary hard drive can be installed internally or externally in most computers. The computer recognizes the drive as an additional storage device and by default assigns it the first unassigned drive letter for identification purposes. Internal drives can be installed using standard IDE connections or serial ATA connections if the motherboard supports SATA. External drives connect to the computer using USB, FireWire or an external SATA port.
  
  

Additional Storage

• Adding additional data storage space to a computer is one of the more common reasons for installing a second hard drive. The additional space can also make it easier to organize certain types of data; programs and system files can be placed on the primary drive while music, documents, pictures and other media files can be placed on the secondary drive. When installed, the actual capacity of each drive will be slightly smaller than the advertised capacity due to formatting.
  
  

Data Protection

• Using two hard drives protects data by creating a physical barrier against data loss in the event of hard drive failure. A secondary hard drive can be used to store backups of operating system data, important documents and other files that would be difficult to replace in the event of a hard drive crash. Users can set up automatic data backups in their operating systems or can copy important files to the secondary hard drive manually.
  
  

Dual-Boot Systems

• If a computer has two operating systems installed, two hard drives allows the user to give each OS a dedicated drive for its files. This ensures that data will not accidentally be overwritten when one operating system saves files or settings information to the drive it is stored on. Each OS will view the drive where it is installed as the primary hard drive on the system when it is booted up.
  
  

Partitioning

• Some computer users with large capacity hard drives choose to partition their drives instead of purchasing a second hard drive. Each partition is recognized as a separate hard drive by the computer's operating system even though the partitions share the same physical drive. A single drive can support multiple partitions, with each partition serving a different purpose such as storing specific file types or acting as the default save location for different operating systems on a multi-boot computer configuration.
  
  

Laptop Hard Drives

• Some models of laptop computers allow a second internal hard drive to be installed or come equipped with two hard drives. Internal laptop hard drives may connect with IDE or SATA connections depending on the model of the laptop, and may come in one of several size configurations. External hard drives that connect via USB can be used with laptop computers, and some laptops may feature an external SATA port as well so that eSATA external drives can be connected. Laptop compatibility should be checked before purchasing an internal hard drive.