How To Fix 0x803FA071 on Windows 10 Anniversary Edition (Version 1607) or later
Reader Question:
“Hi Wally, I installed a new motherboard but kept the old hard drive with genuine activated Windows installed in it. Now, when the computer is telling me that the product key is already in use Error code: 0x803FA071. How do I fix this?” – Darrell G., USA
Before addressing any computer issue, I always recommend scanning and repairing any underlying problems affecting your PC health and performance:
- Step 1 : Download PC Repair & Optimizer Tool (WinThruster for Win 10, 8, 7, Vista, XP and 2000 – Microsoft Gold Certified).
- Step 2 : Click “Start Scan” to find Windows registry issues that could be causing PC problems.
- Step 3 : Click “Repair All” to fix all issues.
Setting up weekly (or daily) automatic scans will help prevent system problems and keep your PC running fast and trouble-free.
Wally’s Answer: Sometimes even experienced PC users can make mistakes. Windows has always supported a wide variety of hardware. This makes it possible to use one installation of Windows on another computer.
However, modern versions of Windows are attached to hardware. So, making major changes in hardware warrants reactivating Windows.
Note: This will not work for activating Windows on two different computers. One copy of Windows can only be used on one computer at a time.
Problem
The user took a computer with an activated copy of Windows 10 and made major changes to its hardware (or moved the hard drive to a different computer). Now, Windows does not run normally, showing an error saying:
This product key is being used on another PC. Please try a different key. Error code: 0x803FA071
Cause
Modern versions of Windows store the computer’s hardware details so that one key can only be used on one set of hardware. Therefore, if major changes are made to the hardware of the computer, then Windows will show error 0x803FA071
Solution
Here are a few ways to fix the 0x803FA071 error:
Reactivating An Early Version of Windows 10 (Before Version 1607)
Reactivating Windows 10 before the Anniversary edition (Version 1607) is different than Reactivating Windows after the Anniversary edition (Version 1607).
If you are using an older version of Windows 10 which has not been updated yet, then you may need to use the instructions for that older version which you can find by clicking here.
How To Re-Activate Windows 10 Anniversary edition (Version 1607 and Later Versions)?
Press the Windows Key to open the Start Menu and click Settings.
Click Update & Security
Click Activation, and then click Add an account
Enter your Microsoft Account login details. If you used a local account to Activate Windows the last time, then you’ll need a local account login here as well.
Once you enter the correct login details, you should see a message telling you that Windows is activated with a digital license linked to your Microsoft account when you go to the Activation page.
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Is Your PC Healthy?
I always recommend to my readers to regularly use a trusted registry cleaner and optimizer such as WinThruster or CCleaner. Many problems that you encounter can be attributed to a corrupt and bloated registry.
Happy Computing! 
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About the Author
Wally PhillipsWindows Wally is a helpful guy. It’s just in his nature. It’s why he started a blog in the first place. He heard over and over how hard it was to find simple, plain-English solutions to Windows troubleshooting problems on the Internet. Enter: Windows Wally. Ask away, and he will answer.
