How to Install an Operating System on an External Hard Drive

By Jeffrey Ober

Updated September 28, 2017

Items you will need

  • Operating system installation disc

  • CD/DVD-ROM drive for operating system installation disc

Installing an operating system on an external hard drive can help you have more options with your computer. It can also be done if you are having a lot of problems with the internal temperatures of your computer—a hot hard drive will not last a very long time. In order to get your operating system onto an external hard drive, you first have to set up the hard drive mechanically, and then you can work on getting the operating system installed.

Connect the external hard drive to your computer. Install the interface card in your computer, connecting the interface card to the hard drive and attaching a power supply to the external hard drive. Be sure that you put the hard drive in a stable location with plenty of air flow. If it falls down from where you place it, the drive may crash and never work again.

Adjust your BIOS to recognize the external hard drive. When your computer starts up, follow the instructions on the screen to enter your BIOS setup program. This may be the "Del," "F10," "F12" or some other key. Once you are in the BIOS setup, find information about hard drives and change your configuration to see the external hard drive. In many cases you can have the BIOS automatically detect your new hard drive.

Insert the operating system installation disc. Place this in your CD/DVD drive before you exit the BIOS setup.

Exit your BIOS setup and allow the computer to reboot. It should boot from the operating system setup disc.

Follow the operating system installation instructions. Each one will have a different set of instructions. Follow those instructions, but be sure to select your external hard drive when the operating system asks which hard drive to install to.

Re-configure the BIOS setup. Once the operating system is installed on your external hard drive, you may need to tell the BIOS to use that disc as your boot disk. If it is the only disc on your computer, it will boot from it automatically. If you still have internal hard drives, you will once again need to enter your BIOS setup program and inform the BIOS that you want to use this new device as your boot device.

Reboot your computer and watch your new operating system start up.


If you already have an operating system on an internal hard drive, be sure you know how to identify each drive in BIOS to avoid confusion when installing the operating system.


Installing an operating system on a drive will completely erase all information on that drive.