The blog of Windows Wally, a Windows Support Technician helping common people solve frustrating computer problems.

How To Do A Clean Install Of Windows 10 From Windows 7 or Windows 8?

Reader Question:

Hi Wally, 

Please help. How can I make a clean install after upgrading to Windows 10?? By old Windows 7/8 key isn’t working. I read online that once you use the media creation tool from Microsoft and upgrade to Windows 10, the old key is upgraded to a Windows 10 key.

If this is the case then why am I not able to use it. Why is it showing up as an invalid key?? I made an ISO and tried a clean install with it but it doesn’t work!! I ignored the part when it tells you to enter the key but it later asked for the key again. I put the key in and ”this key doesn’t work”. How am I supposed to install Windows 10??

- Kimberly K., Australia

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: Windows 10 has really soared in popularity since its release. Many users are upgrading from Windows 7 or Windows 8 as usual but some users have different demands. Many of us old users know that an upgrade is never as good as a clean install so I understand why you would want to install Windows 10 like this. Although Windows 10 upgrades seem to be running pretty stable so far.


I can upgrade from Windows 7 or Windows 8 to Windows 10, but why can’t I do a clean install?


Because you tried to use your old key. You’re not supposed to enter a product key at all. Just skip it, and let the installation finish.


Here is why you couldn’t do a clean install of Windows 10:

What Happens When You Upgrade To Windows 10?

Whether you have Windows 7 or 8, if Windows is activated then it has already been registered with Microsoft. When you upgrade to Windows 10 your computer’s hardware is checked in Microsoft’s databases against the Windows 7 or 8 product key and then a Windows 10 certificate is created. This certificate is then stored with your computer’s hardware and Windows 7 or 8 product key.

You won’t get a Windows 10 product key, only a generic key but you can’t use this key on another computer.

How To Perform A Clean Install Of Windows 10

If you want to perform a clean install of Windows 10 on a computer, you should already have upgraded it to Windows 10. You can do this using the Windows update feature in Windows 7 or 8.

Windows 10 - Windows 10 - Installation -- Windows Wally

Of course, you’ll need to make a bootable installation DVD or USB from an ISO to install Windows 10 from scratch. You can get it by downloading the Media creation tool from Microsoft by clicking here.

Once you have a bootable installation disk, you should be able to install Windows 10 using the clean install feature. When it asks for the key, ignore, and continue.

Later it should ask for a key again and look for your computer’s information on Microsoft’s servers. Once it finds that your computer was upgraded, it should continue with the installation and activate Windows 10.

I Hope You Liked This Blog Article! If You Need Additional Support on This Issue Then Please Don’t Hesitate To Contact Me On Facebook.

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

Windows 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.