By Ivy / Last update August 27, 2021

Cloning hard drive is the fastest way to help users replace old hard drive , install OS on a larger disk or boost the performance of a computer. Meanwhile, you don't need to spend much time and effort to reinstall Windows and programs. The same goes for cloning windows 10/8/7 to an external disk. This is a case taken from the internet. 

Can I clone a hard drive with Windows 10 on it?

I have a computer with Windows 10 preinstalled. But the hard drive for my computer run out of space and I want to clone Windows 10 (including OS, installed app, drivers, etc.) to external hard drive. Can I clone entire Windows 10 to an external hard drive and boot from the cloned drive?  Any kindly advice will be appreciated.

No matter what your purpose is, you can clone Windows 10/8/7 to external hard drive effortlessly with the best disk cloning software. Here is a quick navigation for this article, you can directly click the anchor text to learn more. 

Why do you clone Windows to external hard drive?

For cloning hard drive in Windows 10, 8, 7, different users may have different reasons. Here, I’ll introduce you the common used reasons for this operation.

  • Upgrade old disk to larger disk or SSD. After long time use, your disk is old and fragile, and has insufficiant space, which may greatly reduce the performance of your computer. Therefore, you need to clone disk to larger disk or upgrade to SSD. It's said, an SSD is 10 times faster than the common HDD.

  • Retain a backup copy on external hard drive for disaster recovery. The cloned disk can be regarded as a simple backup, because you can directly replace HDD without restoring a system/disk image when your computer runs into issues.

  • Avoid reinstalling Windows from scratch. Reinstalling Windows will delete everything during the process and install a fresh copy of system for you. Therefore, after reinstalling, you still need to install required drivers, and programs you will use in the near future. What's more, your files will go forever if you don't backup it first.

What is the best software to clone a hard drive?

It is disappointing that Windows does not have disk cloning software, so you can only ask for help from third-party tools. I highly recommend you AOMEI Backupper Professional to copy Windows to external hard drive because of its advantages in the following.

  • Compatible with all operating system, including Windows 10, 8.1, 8, 7, XP 

  • Clone hard drive with different size: This software allows you to clone hard drive to larger drive as well as clone larger HDD to smaller SSD. The later one requires target disk has nough space to include all sectors of the source disk. 

  • Clone hard drive with different partition style: Some software only allows you to clone hard drive with the same partition style, ie, GPT to GPT or MBR to MBR. But, in this software, you can clone GPT disk to MBR, and vice versa.

  • Adjust partition size of destination disk with "Edit Partitions": This feature is to fix cloned hard drive show wrong size when you clone disk to larger disk.

  • Clone all sectors with "Sector-by-sector clone": By default, this sofwtare only clone used sectors, which is widely used in cloning large hard drive to smaller drive. But you can choose to clone all sectors of the disk to a larger one, whether used or not. 

  • Boost SSD performance with "SSD Alignment": This feature is designed for SSDs to get higher performance, such as, faster reading and writting speed, longer service life. 

Example: how to clone Windows 10 to external hard drive?

Before cloning hard drive in Windows 10, you need to do some preparations:

  • Connect the external hard drive with your computer. If it's a laptop, you may need a USB-to-SATA cable to connect for cloning.

  • Check the disk space of both disks. Logically, the target disk needs to be larger than or equal to the source disk. If not, the cloning process may fail.

  • Backup files to external hard drive before cloning, because the external hard drive will be overwritten finally. If there are any important files, you will lose them.

  • Download and install AOMEI Backupper Professional. Please make sure it can be detected.

Download Free Trial Win 10/8.1/8/7/XP
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To clone Windows 10 to external drive, use the following steps:

Step 1. Open this utility, and select “Clone” and “Disk Clone” in the main page. This option will clone computer to external hard drive in its entirety, if you want to clone only OS, please click “System Clone” instead.

Choose Disk Clone

Step 2. Select the internal hard drive of Windows 10 and click “Next”.

Select Mbr Disk

Step 3. Select the external hard drive you prepare and click “Next”.

Select Gpt Disk

Step 4. Click “OK” to continue this operation if you are aked to backup all partitions on the destination disk.

Backup First

Step 5. Tick "SSD Alignment" if the external hard drive is an SSD. Tick "Edit Partitions" to adjust partition size of target disk if it's larger. Then, click “Start Clone” to copy Windows to external hard drive and wait for final result.

Preview Clone

◉ Don't use external SSD or hard drive as a boot drive, because the USB-to-SATA adapter does not provide enough power supply required for boot. Therefore, please install the external disk internally first.
◉ AOMEI Backupper Professional only support Windows 7/8/8.1/10/XP/Vista. Therefore, if your computer is server 2008/2012/2016/2019 etc, you could consider using AOMEI Backupper Server.

How to boot from cloned hard drive?

After cloning Windows to external hard drive, the process is half done. All you need to do is to replace the old disk and see if your computer can boot from the cloned drive. To boot from the external HDD or SSD, follow the steps below.

Step 1. Open the drive bay. Shutdown your computer, plug out all power, remove the hard drive bay cover with a screwdriver.

Step 2. Take out the original hard drive. Unscrew the screws holding the hard drive, then take out the existing hard drive at an angle(eg: 30 or 45 degrees).

Take Out Original Hard Drive

Step 3. Installed the external hard drive back into your computer.

Step 4. Change boot order after replacing hard drive and boot from it. 

Turn on your computer, hit the specific key in the initial screen (usually F2 or ESC) to access BIOS, go to the boot tab and use “+” to move the external drive to the first option, then press “F10” to save the change and boot from the cloned drive.


Written in the end

With the help of best disk cloning software like AOMEI Backupper Professional, cloning Windows 10/8/7 to external hard drive becomes simple and efficient. Thanks to its intuitive interface, most users can understand all the steps easily and quickly. You can not only use it to copy hard drive to another one, whether larger or smaller. More so, it will run this task in the background without interrupting your work.

Besides, this utility is still a Windows backup utility, which allows you to backup system/disk/partition/files, create incremental/differential backup, perform event trigger backup, create bootable USB, dissimilar hardware restore, mirror folder to network drive, sync local folder to Google Drive etc. Why not give it a try right now?