Reasons to clone Windows to an external hard drive

Have you ever been in this situation where your computer is old and you need to replace it with a new one? It takes a long time to reinstall Windows on the new computer. Some non-professionals don’t even know how to reinstall the system. Then, cloning Windows to an external hard drive as portable Windows can be the best solution.

In addition to the situation mentioned above, you will encounter many situations that require copying Windows 10/8/7 to an external hard drive. There are three main aspects as below.

  • Keep the cloned external drive as a system backup drive. You'd better copy OS to an external hard drive in case some bad things happen like: system crash, virus attack, and human error, etc.

  • Hard drive upgrade. You may need to clone Windows to a larger drive for a big capacity or clone Windows to an external SSD for a good performance.

  • Convenient to carry. You might prefer to clone Windows to a USB drive or CD/DVD because of their light weight. Therefore, you can carry the portable Windows easily.

Best cloning utility to clone OS to an external hard drive

Since Windows doesn't provide a direct way to clone your system, you have to turn to some third party programs. AOMEI Backupper Professional has to be mentioned here. This is a powerful uitility that permits you to clone Windows to an external hard drive in a few simple steps. Windows 10/8.1/8/7/Vista/XP are supported.

By default, this program performs an Intelligent Clone, which enables you to copy only used sectors to the target drive. Thus, you are allowed to clone Windows to a samller drive, for instance, clone Windows 10 to smaller SSD. Additionally, it works well to improve working performance of your SSD when migrating OS to an SSD in Windows 10/8/7. More pleasing, it has an intuitive intferface which makes this utility very easy to use. Let's see how it works.

Example: How to clone Windows 7 to an external hard drive?

Before you do so, connect the external hard drive with your computer. After cloning, the external hard drive will be overwritten. If you have stored some important files on it, you'd better backup files to external hard drive.

Step 1. Install and open this utility. Select Clone from the left list. Then click System Clone.

System Clone

Step 2. The required system partitions are selected by default. Select the external hard drive (Disk 2) as the target drive. Then click Next.

Select New Location

Step 3. At this interface you can have an Operation Summary. If all things are right, you can click Start Clone.

Click Start Clone

Step 4. After cloning, you can get your external hard drive out.


  • You can enter into BIOS and set the external hard drive as the first boot disk.

  • Sector by sector clone: all sectors will be cloned. Ensure that the external hard drive is equal to or larger than the space of the system.

  • If you use an SSD as your target drive, you can click Align partition to optimize for SSD at Step 3 to accelerate the writing and reading speed of the SSD.

  • The old drive will not be wiped out, you can keep it as a backup or reformat it for other purposes.

  • The above steps also work with Windows 10/8.1/8/Vista/XP.


It is not hard to clone Windows to external hard drive, isn’t it? AOMEI Backupper Professional is not only easy to operate, but also offers you many advanced options. The cloning process will not interrupt your work, so you can still use your computer to do other things while copying. Besides, this utility also offers you many flexible backup solutions, for example, automatic old backups' cleanup. But if you are a Windows Server user, AOMEI Backupper Server is helpful.