If you've upgraded your laptop or PC with an SSD, its old hard drive might be sitting unused. For little money, you can install it in an external enclosure and use it as a portable USB drive. Here's how.

What is an external enclosure?

Hard drive caddies - or enclosures - are inexpensive and allow you to turn an internal hard drive into an external one that you can use for backing up files, or even to attach to your smart TV so you can pause programmes or record them (if it supports those functions).

You'll need to buy the appropriate caddy for your particular drive, but there are two main types: 3.5in and 2.5in. Also see: Best NAS drives.

3.5in hard drives are mainly used in desktop PCs, while 2.5in disks are used in laptops. Laptop hard drives vary in thickness (either 7mm or 9.5mm), so make sure your chosen caddy has enough height inside to accommodate your disk.

We're using a standard 9.5mm drive here and an Inateck enclosure, which you can buy for £10.99 from Amazon and will accept both 9.5mm and 7mm drives, including SSDs as well as traditional hard drives.

It's a USB 3 enclosure, and it's well worth spending a few pounds more over a USB 2 version as they can be up to 10 times faster when connected to a USB 3 port on a PC or laptop.

Most hard drives use the modern SATA connector (you can see this in the photo below), but older hard drives have IDE connectors with two rows of gold-coloured pins. Again, make sure you buy an enclosure which is compatible with your drive. 

How to install it

Step 1: If you haven't already done so, remove any brackets and screws from the hard drive.

How to use a spare internal hard drive as an external hard drive

Step 2: Open up the caddy: the Inateck FE2005 we're using is a tool-less model, so it's a simple case of unlocking it with the switch, sliding open the end and inserting in the hard drive. Be careful to slide the hard disk in the right way up - look inside to see the orientation of the SATA port.

How to use a spare internal hard drive as an external hard drive

How to use a spare internal hard drive as an external hard drive

Step 3: Use the included USB cable to attach the enclosure to your PC or laptop.

Step 4: Depending on what's on the disk, it may show up in Windows File Explorer and be ready to use. Because our disk was from a Windows laptop, it was formatted as NTFS and was assigned a drive letter automatically.

You can treat it like any hard drive, copying files to it, or formatting it. If you plan only to use it with Windows, you can leave it formatted as NTFS, but it's best to use exFAT if you want to connect it to other devices such as set-top boxes for video playback.

What you might not want is for the drive to show up as two disks, as ours did due to a 100MB system partition from the old Windows installation.

We'll deal with this in the next step, which also applies if your disk doesn't appear when you connect it.

How to use a spare internal hard drive as an external hard drive

Step 5: If it doesn't show up in Windows Explorer, search the Start menu for Disk Management and then look for a disk with unallocated space, or a disk without a drive letter assigned. You can then right-click on it and format it.

How to use a spare internal hard drive as an external hard drive

If, like us, you need to remove an unwanted 'System Reserved' partition, just right-click on it and choose Delete Volume. It will then be unallocated space, and since it's only 100MB, we will just leave it unused.

How to use a spare internal hard drive as an external hard drive

Can I get a USB-C enclosure?

Yes you can. USB-C ports are slowly becoming the standard and you'll find these on the latest PCs and laptops including the new MacBook.

Aukey sells an enclosure that you can buy for £14.99 from Amazon UK (or $15.99 from Amazon US).

Aukey USB-C external enclosure

Theoretically the USB-C connection on this caddy can operate at up to 5Gb/s or 625MB/s, but it will be limited by the hard drive you put inside it.

It's simple to install your drive. As before you should check that you are inserting it the correct way around - check the orientation of the SATA connection. You can then use the included USB-C to USB-C cable to attach the portable drive to the USB-C port on your PC. No drivers are needed, so it should be a simple case of plug and play.