Shop around online and it won’t be long before you come across cheap versions of Windows 10 on sale. Some of these will no doubt be of a dubious nature, while others seem legitimate. So, what are these odd-sounding versions such as OEM, and should you buy one for your PC? We break it down.

What is an OEM licence?

OEM stands for Original Equipment Manufacturer and is a term applied to companies that build PCs. These devices usually include a copy of Windows, so that when you walk out of Currys/PC World with that shiny new Dell you can take it home and use it immediately.

These versions of Windows are more often than not OEM copies, in that they have been sold to the manufacturer at a discount so they can be put on their PCs.

While the majority of OEM versions end up preinstalled on PCs, it’s also possible to buy them as licence keys from places like eBay or Kinguin. This is a common practice for users who like to build their own gaming PCs, or buy a second-hand device that has either no OS, or one that is out of date.

How is an OEM licence different to a retail version of Windows?

Most people never buy a copy of Windows itself. They buy a PC that has Windows on it, and that’s the last they think of it.

But those who do want to purchase the operating system often opt to pick up a retail version. These are either sold in standard software packaging in shops, and thus called boxed copies, or are available online from Microsoft as a download and licence key.

Microsoft's price for a download version of Windows 10 is £119.99. Compare that to eBuyer's £96.54, or the even cheaper options online over on Amazon. Kinguin's price for a Windows 10 Pro OEM key is just £24.87, or from £20.87 for the Home Edition.

 Whats difference between Windows 10 OEM and retail versions

In use, there is no difference at all between OEM or retail versions. Both are full versions of the operating system, and as such include all the features, updates, and functionality that you would expect from Windows. 

Where their paths diverge is in two important areas: support and flexibility.

When you buy an OEM copy you’re in essence taking on the role of the manufacturer of your device. This means that if you run into problems with hardware compatibility or encounter activation issues, calling Microsoft for help will probably end up with you being told to contact the manufacturer of your device. Which, of course, in this case is you!  

The second major difference is that whereas when you buy a retail copy of Windows you can use it on more than one machine, although not at the same time, an OEM version is locked to the hardware on which it was first activated.

This might not seem a major issue, but if you decide to change the motherboard on your PC, then chances are you’ll also need to pay out for a new copy of Windows at the same time, as the old one won’t re-activate on the new hardware.

To see how you can reuse your retail Windows licence read our How to install Windows on more than one PC feature.

Should I buy a cheap OEM key?

There’s nothing illegal about buying an OEM key, so long as it’s an official one. There are plenty of legitimate sites online that deal in this kind of software, Amazon has a number of sellers offering OEM keys, as does eBay, and more specialist sites like the aforementioned Kinguin.

Just be sure to read the description carefully and check user ratings before spending any money.

So long as you’re happy to take on the responsibility of being your own technical support, then an OEM version can save a lot of money while offering an identical experience.

Of course, those who prefer peace of mind, and someone at the end of the telephone who can help fix any problems, might prefer the full retail route instead. Just avoid buying a DVD version from that dodgy-looking guy in the Tesco car park.