How to upgrade an old PC to Windows 10 - free
[This article has been completely rewritten to incorporate developments in later updates to Windows 10. The most recent update was published May 26, 2018.]
If you purchase a new PC with Windows 10 Home preinstalled, prepare to be annoyed. This down-market edition (maybe we should just call it Windows for Cheapskates) doesn't have the features you need for getting real work done: Remote Desktop server access, BitLocker disk encryption, group policy support, and control over when updates get installed, just for starters.
You could pay $99 for an upgrade, but before you reach for your wallet, consider a less expensive option.
Do you have an old product key from Windows 7 Pro, Windows 7 Ultimate, or Windows 8/8.1 Pro lying around? Those keys can be reused to enable an upgrade from Windows 10 Home to Windows 10 Pro, potentially saving you the upgrade fee. In fact, you can use a product key from any of these older Windows versions to perform a clean install or to upgrade to Pro.
It's worth rummaging through your garage, storeroom, or email archives to see if you can locate one of those old keys. Maybe you still have a key for one of the heavily discounted upgrades to Windows 8 Pro that Microsoft offered in the first few months after that product's ill-fated launch in 2012.
Or perhaps you have a shrink-wrapped retail copy of Windows 7 Professional or Ultimate, where the license associated with the product key is no longer in use.
In fact, you only need to use the older product key one time. After you upgrade from Windows 10 Home, the Windows 10 Pro digital license is attached to the specific hardware you just upgraded, allowing you to reinstall that edition of Windows on that hardware anytime, without the need for a product key.
This scenario worked during the early Windows 10 upgrade program, and after some testing and multiple reports from independent testers worldwide I can confirm that it still succeeds in mid-2018.
Microsoft first made this option available in Windows 10 version 1511. Since then, they have simplified the process dramatically.
I've been testing upgrade/activation scenarios on a wide variety of hardware recently to see how things work. Here's the scoop.
UPGRADING A NEW PC FROM HOME TO PRO
Let's say you buy a new PC with Windows 10 Home installed by the OEM. Some vendors offer an upgrade option as part of the purchase, but many PCs sold in the retail channel are preloaded with Home edition.
This could also be the case if you took advantage of the free Windows 10 upgrade offer on a PC running a Home edition of Windows 7 or Windows 8.x.
In either case, the upgrade takes just a few minutes. Start at Settings > Update & Security > Activation, where you should see a screen that looks something like this:
If you don't have a Pro product key and you want to buy one, you can click Go to the Store and purchase the upgrade for $100. Easy.
But if you have a product key for Windows 10 Pro, Windows 7 Professional or Ultimate, or a Windows 8/8.1 Pro, you can click the Change Product Key button and enter it here.
Using an older version's product key to perform this upgrade used to require two steps. Fortunately, in recent feature updates this two-step process isn't necessary.
After entering the product key, follow the prompts to perform the upgrade.
You'll see a succession of progress screens and your system will restart. After the upgrade completes, you should see a Success notification. Check the Activation screen again to confirm that you're now running Windows 10 Pro.
After you've successfully performed a Home-to-Pro upgrade, you can safely throw away the key. Your upgrade is now a digital license, attached to your unique hardware. If you perform a reinstallation of Windows, Microsoft's activation servers will recognize the hardware and activate Windows 10 automatically.
I tested this scenario by upgrading the SSD in an HP Spectre x360 that originally shipped with Windows 8.1 Home and had then been upgraded to Windows 10 Pro. After the upgrade was complete, I used a USB flash drive to reinstall a clean copy of Windows 10 Pro.
Twice during the installation process, I was prompted to enter a product key. Both times I chose the option to skip entering the key. When prompted, be sure to choose Windows 10 Pro as the edition to install.
When setup was complete, I signed in and checked the activation status (Settings > Update & Security > Activation). The system was properly activated, because Microsoft's servers recognized the hardware and used the digital license.
CLEAN REINSTALL, WITH EDITION UPGRADE
The one gotcha in this series of scenarios comes when you have a system that includes digital licenses for both Windows 10 Home and Windows 10 Pro. In that scenario, you can inadvertently restore Windows 10 Home.
This happened during my testing when I used the recovery image for a PC that originally shipped with Windows 8.1 Home and then upgraded the restored PC using Windows 10 recovery media. Not surprisingly, I ended up with an installation of Windows 10 Home.
If that happens to you, don't bother searching for your original product key. Instead, use Microsoft's generic product key to force the upgrade.
Go to Settings > Update & Security > Activation and click Change Product Key. Next, enter the default Windows 10 Pro product key:
Follow the prompts to upgrade from Home to Pro. Because your hardware already has a digital license for the Pro edition, it will activate automatically.
That generic product key isn't magical, of course. If your hardware doesn't already have a Pro license, you'll get an activation error and you'll need to supply a proper product key or pay for an upgrade.