When you purchase a computer that comes with Windows 7, Windows Vista, or Windows 8, that copy of Windows is tied to your computer's hardware. It's an OEM copy, which means it can only be used on that computer. Even if you purchase a retail, boxed copy of Windows and install it, that copy of Windows will become tied to your hardware after it activates itself with Microsoft. If you change your hardware later, your copy of Windows may become "non-genuine," turn your desktop background black, and start pestering you to use a genuine version of Windows.

You're allowed to make certain hardware changes under the Windows license agreement, but even making allowed hardware changes may turn your copy of Windows into a "non-genuine" copy that requires reactivation with Microsoft.

Why Windows May Become Non-Genuine

Windows becomes non-genuine after some hardware changes to prevent you from taking a copy of Windows tied to one computer's hardware and move it to a new computer. This sounds simple, but, in reality, it's hard to define exactly what a single computer is. Is your computer still the same computer if you change its graphics card? Sure, probably. What about the motherboard and CPU? Maybe. What if you change the motherboard, CPU, memory, and everything but the hard drive? Where exactly do you draw the line between the old computer and a new computer?

Microsoft doesn't spell out the exact hardware changes that can cause a Windows PC to become non-genuine, but we know that changing the following hardware components can cause this: The motherboard and CPU, hard drive, network card, graphics card, and RAM. Changing a single component or even two components may be fine, but changing several components may upset Windows. In some cases, changing a single component -- like imaging a failing hard drive, replacing the hard drive, and then re-imaging your copy of Windows to that hard drive -- may result in Windows becoming non-genuine.

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Allowed Hardware Upgrades

Before you continue, it's important to bear in mind what's allowed and what isn't. This will depend on whether you have an OEM (Original Equipment Manufacturer) or retail copy of Windows installed on your computer.

  • OEM Copy: If your computer came with Windows, it likely has an OEM copy. An OEM copy is tied to a specific computer and can't be moved to a new computer. While you're free to upgrade a PC's hardware components or replace a failing hard drive, you can't move your OEM copy to a new computer.
  • Retail Copy: If you purchased a boxed copy of Windows, it's likely a retail copy. A retail copy of Windows can be moved to a new computer, but you're only allowed to use that copy of Windows on a single computer at a time. That means you'd have to uninstall the old copy of Windows before you moved it to a new computer.

It's important to understand these limitations. For example, if your computer is non-genuine because you've attempted to move a hard drive containing an OEM copy of Windows to an entirely new computer, Microsoft won't help you make that copy of Windows genuine again. Even if you have a retail copy, you'll want to ensure it's only installed on one computer at a time.

Many online stores seem to sell OEM copies of Windows in boxes. This isn't technically allowed via Microsoft's license agreement, but if you do buy such a box, you won't be allowed to move it to a new PC after installing it on a PC.

This is all the way it's supposed to work, according to the Windows license agreement. However, if you call and ask nicely, Microsoft may allow you to move an OEM version of Windows to a new computer -- that's their prerogative. Many people have noticed that Microsoft is more flexible than the language in their license agreements would lead you to believe.

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How to Make Your PC Genuine Again

If you do find yourself with a non-genuine version of Windows after performing a hardware upgrade, replacing a failing component, or -- in an extreme worst case scenario -- upgrading a hardware driver or firmware that causes Windows to think you're using a new component, you'll need to activate Windows again with Microsoft.

To re-activate a Windows 7 PC, you'll need to open the Windows Activation tool. To do so, click the Start button, type "Activate" into the Start menu, and click the Windows Activation shortcut. Select the "Show me other ways to activate" option and go through the wizard, selecting the "Use the automated phone system" option. You'll then be given a toll-free number you can dial. If everything goes properly, you'll be given a confirmation ID you can enter into the Windows Activation tool to make Windows genuine again. If the automated system fails, you'll be put on the line with a Microsoft customer service representative. Explain your situation and they'll hopefully allow you to re-active your installed copy of Windows, making it genuine again.

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Of course, there are also other unofficial methods, one of which James covered here in the past. These hacks may allow you to bypass the Windows activation system. We don't really recommend using them. For one thing, it's against Microsoft's license agreement. What's more, such tools may not be completely secure -- you're downloading and installing a tool that requires low-level access to your system from a shady website that you can't completely trust. And, if you have an actual legitimate copy of Windows, Microsoft will likely be happy to make it genuine again if you go through the activation process and give them a phone call.

Have you ever had Windows become non-genuine after upgrading or replacing a piece of hardware? Did you have any trouble re-activating Windows with Microsoft? Leave a comment and share your experiences!

Image Credit: Eric Jones on Flickr