How to Add a Second Hard Drive to a Computer

by Jeff Grundy
Adding an external hard drive takes just a few minutes, while installing an internal drive takes about half an hour in most cases.

Adding an external hard drive takes just a few minutes, while installing an internal drive takes about half an hour in most cases.

Back during the days when Windows 3.11 ruled the desktop operating system market, many users considered a hard drive capable of storing a few hundred megabytes huge. These days, however, even drives with several hundred gigabytes of storage space may not suffice for the voluminous data users create and download in the form of music, photo and video files. Even the largest multi-terabyte drives fill up quickly with HD-format videos. Consequently, you might need to add a second hard drive to your computer to keep from using all the space on your primary system drive. In addition to giving you extra storage space, adding a second internal or external hard drive can also help performance by reducing clutter and fragmentation on your main drive.

Adding an External USB Hard Drive

Plug the AC adapter into the power connector port on the external hard drive if it requires one - not all do. Plug the other end of the AC adapter into an available electrical outlet.

Plug the small end of the data cable into the mini-USB on the side or rear of the external hard drive, then connect the other end of the cable into an available USB port on the computer. Wait a few seconds while Windows recognizes and configures the external hard drive as removable storage drive for your PC. Note that Windows does not require any special drivers for USB external hard drives, as it has the necessary software already built-in to the operating system.

Click Start, then “Computer" to open Windows Explorer. Right-click the drive letter assigned to the external hard drive by Windows, then click “Format” on the pop-up option menu. In the Format window, select the “NTFS” format type, then click the “Start” button to format the external hard drive.

Use the external USB hard drive to save or back up documents and other files just as you would the primary system drive in your computer.

Installing an Internal Hard Drive

Power off the computer and disconnect all attached cables and peripherals. Move the computer case to flat surface and place it on its side so that the access panel faces upward.

Use the Phillips screwdriver to loosen and remove the case retaining screws on the rear of the computer that secure the access cover in place. Some covers are secured with only a thumbscrew. Slide the cover off the case and set it aside.

Locate the 3.5-inch drive bays inside the case near the front panel of the computer. In most desktop computers, the drive bays should be below the bays used to house the CD/DVD and floppy drives. Slide the anti-static wrist strap onto your arm and clip the other end to one of the metal drive bays inside the computer case.

Select one of the empty 3.5-inch drive bays and slide the new hard drive into it. Use the mounting screws that shipped with the hard drive to secure it inside the drive-mounting bay.

Locate an available 4-pin 1.5-inch Molex power leading from the power supply if using an IDE drive. If using a SATA hard drive, locate the power connector from the power supply that resembles the ribbon cable used to connect the drive to the motherboard. Plug the appropriate power cable into the power port on the rear of the hard drive.

Plug an IDE or SATA ribbon cable (depending on the type of drive you install in your computer) into the data port on the rear of the hard drive. Plug the other end of the cable into the matching port labeled "SATA 2" or "Secondary IDE" on the computer's motherboard -- again depending on the type of drive you install in the computer. The cables only fit into the port receptacles one way, so there is no need to worry about plugging them in incorrectly. Once you match the cable ends with the port receptacles, they should insert without much force.

Slide the access cover back onto the case and secure it with the retaining screws. Move the computer back to your desk or workstation area and then reconnect all cables and peripherals.

Power-on the computer and press the BIOS access key as soon as you see the initial boot screen. The key needed to access the system BIOS varies depending on the model computer you own. However, keys commonly used to access the BIOS include the "Delete," "F1" and "F2" keys. If you don’t know the BIOS access key for your system, refer to the system user manual.

Enter the BIOS password if prompted to do so. After you enter the BIOS, the computer should detect the new hard drive automatically. Press the "F10" key or click "Exit and Save Changes" to save the new drive configuration and restart the computer.

Log in to Windows with your username and password after the computer restarts. Click Start, then "Computer" and right-click the drive letter for the new drive in Windows Explorer. Windows should display a drive letter for the new hard drive automatically.

Right-click on the drive and click "Format." After the Format window appears, select "NTFS" in the format type drop-down list and click the "Start" button. After Windows formats the new drive, you can use it to store files normally.


  • If your computer power supply does not have a SATA power cable running to it, you can purchase a 4-pin Molex-to-SATA power cable to connect the power supply and hard drive.

Items you will need

  • External USB hard drive
  • USB data cable
  • Internal 3.5" hard drive
  • Phillips #2 screwdriver
  • SATA or IDE cable
  • Anti-static wrist strap

About the Author

Jeff Grundy has been writing computer-related articles and tutorials since 1995. Since that time, Grundy has written many guides to using various applications that are published on numerous how-to and tutorial sites. Born and raised in South Georgia, Grundy holds a Master of Science degree in mathematics from the Georgia Institute of Technology.

Photo Credits

  • Photodisc/Photodisc/Getty Images