Microsoft charges $200 for a Windows 10 Professional product key. But, with a quick search online, you can find websites promising Windows 10 Pro keys for $12 or even less. That’s a huge savings—but don’t fall for it.

Why Are They So Cheap?

The websites selling cheap Windows 10 and Windows 7 keys aren’t getting legitimate retail keys straight from Microsoft.

Some of these keys just come from other countries where Windows licenses are cheaper. These are referred to as “gray market” keys. They may be legitimate, but they were sold for cheaper in other countries. For example, Windows keys were once much cheaper in China.

Other keys could have been purchased with stolen credit card numbers. A criminal acquires some credit card numbers, purchases a bunch of Windows keys online, and sells them through third-party websites at a cut rate. When the credit cards are reported as stolen and the chargebacks occur, Microsoft deactivates the keys, and those Windows installations are no longer activated—but the criminal gets away with the money people paid for them.

Some keys may be education keys intended for students but obtained fraudulently. Other keys may be “volume license” keys, which are not supposed to be resold individually.

On really sketchy websites, you may just be purchasing a completely fake key or an already-known key that was used to pirate Windows on multiple systems that has been blocked by Microsoft. An especially bad website might even steal the credit card number you use to buy the key and use it to start the credit card fraud game anew.

But Do They Work?

A legitimate Windows 10 key would never have issues with “volume activation.”

Okay, okay, so these keys are sketchy. But you’re wondering: Do they work?

Well, maybe. They often do work…for a while.

We once bought a Windows 7 key for about $15 from one of these websites. We stuck it in a virtual machine, and it worked for about a year. After that, Windows started saying we “may be a victim of software piracy.” Our Windows license was no longer “genuine.”

In other words, at some point in that year, the key we purchased was flagged as bad by Microsoft. It was probably purchased with a stolen credit card number, and it was eventually blacklisted on Microsoft’s servers. So it stopped working, and we’d have to buy a new key.

That’s just one anecdote, but it’s our experience. Your key may never work in the first place, it may work for a month, or it may never be blacklisted at all. It all depends on where the key originally came from, and you’ll never know where that was.

These Keys Aren’t Legitimate

These keys just aren’t legitimate. By purchasing them, you may be supporting criminals who steal credit card numbers. Or, you may be rewarding people who abuse programs set up to help students and encouraging the shutdown of these programs.

We all know it: There’s no way a $12 Windows product key was obtained legitimately. It’s just not possible. Even if you luck out and your new key does work forever, purchasing these keys is unethical.

Be Suspicious Anywhere You See a Cheap Key

The keys we’re talking about here are often found on key reselling marketplaces like G2A (G2deal), Kinguin, and many other smaller sites. These sites also sell gray-market video game keys, which are also of questionable origin and may be revoked in the future. Polygon, a gaming website, has a good look at the problem with gray market game keys.

However, you could run into this problem on many websites. Websites like Amazon.com, eBay, and Craigslist are user marketplaces, and it’s often possible to find sellers with Windows 10 or Windows 7 product keys for far too cheap on these websites.

You may have an easier time filing a dispute after buying a shady key from Amazon.com, but just because you buy a $40 Windows 10 product key from someone on Amazon doesn’t mean it’s legitimate. Amazon is a huge marketplace, and it has a problem with counterfeiters. Amazon may not want to help you if your key works for a year before being revoked, either.

RELATED: I Got Scammed by a Counterfeiter on Amazon. Here’s How You Can Avoid Them

How to Get Windows 10 For Free

Okay, let’s say you need a Windows 10 license, and the cheap keys are all you can afford. Here’s what we recommend: Just don’t buy Windows 10.

We’re serious here. You can install and use Windows 10 without a product key. It will show you a watermark and nag you a bit, but you can use it without ever paying anything or providing a product key.

This is a good solution for installing Windows in an occasional virtual machine to test software. It’s also a decent stopgap if you’ve just built a PC and can’t afford a full retail Windows 10 license just yet.

We mean it: You’re better off not buying Windows than buying it through one of these websites.

When you’re ready to buy Windows 10, you can pay to upgrade directly from inside Windows 10’s Store, or by purchasing a legitimate product key and typing it into Windows 10’s Settings app.

RELATED: You Don’t Need a Product Key to Install and Use Windows 10

How to Save Money on Windows 10 Keys

You can still save money on real Windows licenses, too! For example, we just looked, and Amazon is selling legitimate OEM Windows 10 Home licenses straight from Microsoft for $99 vs. the normal Microsoft Store retail price of $139. That’s far from $12, but authorized stores selling real, legitimate licenses often do undercut Microsoft’s prices, so you can find some legitimate savings if you look around.

Better yet, if you have an old Windows 7 or Windows 8 key, you can stillĀ install Windows 10 with that old key. Microsoft will give your PC a free “digital license” of Windows 10. Microsoft is being sneaky and continuing Windows 10’s free upgrade offer with this method.

And, assuming you already have a Windows 10 license, Windows 10’s Settings app can now help you move it between different PCs. So, if you’re switching to a new PC, you may be able to take your current license with you.

You may also be eligible for a program that helps you get a key for cheaper. For example, students may be eligible for cheaper (or free) Windows 10 product keys through their universities.

RELATED: You Can Still Get Windows 10 for Free With a Windows 7, 8, or 8.1 Key

What About OEM Copies of Windows?

When buying Windows keys, you’ll see both “Full Version” or “Retail” licenses and “System Builder” or “OEM” licenses. Many of the legitimate keys sold on online stores like Amazon are “OEM” or “System Builder” keys that lock themselves to a single PC. Retail or “Full Version” licenses are generally a bit more expensive.

Unfortunately, Microsoft’s arcane licensing terms seem to forbid people from using OEM licenses on their own PCs. OEM licenses are only supposed to be used if you’re going to sell the PC, not use it yourself. However, Microsoft has changed its license back and forth over the years, and its messaging has been very confused.

Many average geeks building their own PCs continue to buy OEM copies of Windows for them, and we don’t blame them. Microsoft hasn’t ever tried to stop them, although the OEM license agreement technically forbids it. In fact, Microsoft continues selling OEM licenses to people building their own PCs through stores like Amazon without much up-front warning about the licensing issues.

RELATED: What’s the Difference Between the “System Builder” and “Full Version” Editions of Windows?