Methods to Boot from External Hard Drive

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Sep 03, 2020 • Filed to: Answer Hard Drive Problems • Proven solutions


I had XP and Vista installed on my primary SATA hard drive (on SATA0 channel). There was no space for another operating system, so I added a secondary hard drive (to SATA2 channel) and installed Windows 7 to it. It worked perfectly. After a few weeks, my old primary hard drive suddenly died, and the computer doesn't boot anymore. So I put the remaining live hard drive to the SATA0 channel, and bought another new SATA drive and put it to the SATA2 channel. Now I need to add boot files to my drive because both the operating system and data files are there, I just need to let the computer start.

So I have one good healthy SATA drive, Windows 7 installed on it, but without boot files, because that other (now dead) drive was used to start up the computer. I thought that Windows 7 Installation DVD will help, but it doesn't. When I try to use its repair disk feature, it fails to find any installed Windows, so it says there's nothing to boot to, nothing to repair. If I use the command-line utility from the same DVD, I can see both my C: and D: partitions are there, with all files, I can see all my directories, I can see Windows folder, Program Files folder, etc. But what does it need to boot?

I also tried "upgrade" from W7 Installation DVD, but it says that I should run this option from inside Windows. Since I cannot start Windows, this option isn't for me. When I tried a new fresh installation, I got a warning that all my current data will be overwritten, and that also isn't the option I am searching for. Any advice?

In case if you have to change the priority list on your device and now it is your external hard drive that is acting as a boot drive, then you should know how to boot windows from the external hard drive. It is the same procedure as meant for the internal drive. All you need to know is how to make external hard drive bootable. As not every drive is meant to boot. But making appropriate changes on the drive or in the boot mechanism, you can make any drive bootable. This article will help you to get answers to both of the above-mentioned questions.

Apart from the fact that you get an appropriate answer for how to make external hard drive bootable, a question arises. Why you need an external drive as a boot media for your device. You can make any external media bootable, but using an external hard drive as boot media when you are already having an internal hard drive need special reasons. Here are those reasons:

  1. When windows 10 fails to boot from the internal hard drive. You need an external bootable hard drive for carrying out a boot mechanism. You can change the priority list from BIOS.
  2. Failure of external media can be due to hard drive corruption, bad sectors, or corrupted partitions containing the BIOS.
  3. Virus or malware attack on the drive containing the BIOS information.
  4. In case you are not able to access your device, you can sue the external bootable media on other devices by using your own operating system anywhere anytime.

This article is all about the answer i.e. how to make external hard drive bootable. It also explains the steps for booting external hard drive on windows and mac. Here are the topics that would be discussed in detail.

Part 1: Setting up Your External Hard Drive

In this section, you would get the solution for booting from an external hard drive. This explains all the essentials for setting up the external hard drive to become a bootable media.

1. Figure out your computer’s BIOS key on Windows.

For setting up the external hard drive to become bootable, the first step is to figure out the BIOS key on windows. As for the device, for setting into BIOS settings, we usually press and hold F12. But in case of windows, here are the steps:

Step 1: Launch the search engine. Be it any search engine e.g. google.

Step 2: In the search box, type computer’s manufacturer, name of the model, and phrase bios key. Click enter to continue.

Step 3: Related to your search, the browser will show up certain options. Select the BIOS key that is compatible with your device.

Step 4: Else you can check the device’s manual to search for the BIOS key.

2. Attach the external hard drive to your computer.

In order to make an external drive bootable, it should be kept in mind that the drive should be in constant and appropriate connection with the device. Use a USB cable or free USB port to attach the hard drive with the device. The external hard drive carries an indicator light that either blinks or stabilize when in sound connection with the device. For mac devices, you would need a USB or thunderbolt 3 adapter.


3. Format the hard drive if necessary.

As soon as your external hard drive is an inappropriate connection with your device, make sure the drive should not carry any extra or non-functional data that would otherwise interfere with the boot mechanism. Moreover, if the hard drive is not compatible with the device i.e. the file format on the drive is not compatible, your device won’t be able to read it. In this regard, you can go for formatting the drive into a compatible file system. NTFS for windows and Mac OS extended are preferred file systems. An all-rounder i.e. exFAT file system can be used for both, the windows and mac devices. Once the drive and device are compatible, next you have to reformat your drive according to data going to be stored in it.


4. Make sure you have an item from which to boot.

While in the process to boot the external hard drive. There are some requirements. You need a disc image or ISO file present on the hard drive. Only then you would be able to boot the drive. An empty drive is not bootable. Apart from the ISO (disc image) files, the drive can also carry file history backup for windows or time machine backup in case of Mac that makes the drive eligible for booting.

5. Place the boot file on the external hard drive.

It is not necessary that an external hard drive should itself carry the ISO files to be booted, rather you can drag-drop the ISO files into the external hard drive window. If you are using windows 10 installation tool for creating a bootable media, you can skip this step.


6. Make the external hard drive bootable.

Prior to booting the external hard drive, it is important to at least once view the bootable item. For this, you can sue the command prompt in case of windows or terminal for the mac devices. In case, if you care to sing Linux to burn ISO files on the external drive, then the drive would be booted in the process.


Part 2: Booting from an External Hard Drive on Windows

Every operating system carries its own set of requirements when it comes to boot the external hard drive and then to boot the OS from that external media. So as the case with Windows. This section will tell how to boot from external hard drive windows 10. Here are the steps:

Step 1: Start the process by connecting the external hard drive with the device appropriately. Make sure that your device recognizes the external hard drive.


Step 2: In the windows main menu, click the option of power to restart your device.


Step 3: While your device is in process of restarting, press the BIOS key repeatedly.


Step 4: Your device with a restart in and the BIOS menu will appear on the screen.


Step 5: Select the option of boot order from the list.


Step 6: In the next window, select your hard drive in the boot order list. In some cases, the system only allows the USB attached devices to be recognized in the boot order. So make sure that your drive is only USB storage.

Step 7: Now drag your external hard drive to the top of the list i.e. boot order. Save changes and exit BIOS.


Step 8: Now run any on-screen prompt to open, install, or set the program for the external hard drive. In case you already have an OS installed for the external hard drive, then once you are done with the BIOS setting, the OS will open.


Part 3: Booting from an External Hard Drive on Mac

Booting from an external hard drive on Mac also has a set of instructions. Below mentioned are some of them, just follow the steps and boot from external hard drive on Mac.

Step 1: Initiate the process by attaching the external hard drive with your mac device, make sure the connection is appropriate for that the device could recognize the external hard drive.


Step 2: In Mac main menu, select the option of power, and in the pop up select the option of the restart. Your device will restart.



Step 3: As soon as the screen turns off, press the BIOS key destined for Mac devices. Press and hold the BIOS key until the startup manager window appears on the screen.


Step 4: From the menu, select the external hard drive and confirm your selection. This will mark the external hard drive as the booting media for your operating system.


Step 5: Once the drive is selected, exit the startup manager and follow all the on-screen prompt instructions to open, install, and set up the program. In case you already have the operating system, then as soon as you set the priority setting, the OS will open.


Hence, using an internal hard drive for booting the operating system via it is a common practice. Mostly C drive is the partition that carries all the system files and is destined to boot the OS. But at times, when the operating system fails to boot due to any technical or physical issue to hard drive i.e. bad sector, corrupted partition, and physical damage to hard drive during a disaster, or whole hard drive corruption due to any virus or malware attack. All these situations won’t allow the operating system to work and leaves your device in a non-functional state. In this regard, using an external hard drive for booting the operating system on your device is recommended. This article is all about the details of two important questions i.e. how to make an external hard drive bootable and how to boot from the external hard drive. This article further explains the process for booting from external hard drive on Windows and Mac separately.

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