Great question! As others mentioned, it comes down to the product key embedded in your laptop's UEFI/BIOS firmware — this is called the OEM Activation key (OA3).
Here's how it works:
1. OEM laptops come with a Windows license baked into the firmware at the factory. When you install Windows from a generic ISO (like the one from Microsoft's website), the installer reads this embedded key and automatically selects the matching edition — Home or Pro.
2. Consumer-grade laptops (HP Pavilion, Dell Inspiron, Lenovo IdeaPad, etc.) almost always have a Home key embedded, since manufacturers pay less for Home licenses.
3. Business-class laptops (HP EliteBook, Dell Latitude, Lenovo ThinkPad, etc.) typically come with a Pro key, since enterprise customers need features like BitLocker, Remote Desktop, and Group Policy.
If you want to check what key is embedded in any laptop before installing, open an elevated Command Prompt and run:
wmic path SoftwareLicensingService get OA3xOriginalProductKey
If it returns a key, that's what Windows will use during installation. If it's blank, the installer will ask you to enter a key manually.
And yes — if you have a Home key embedded but want Pro, you can always upgrade by entering a Pro product key in Settings > System > Activation > Change product key. No reinstall needed.