Can't upgrade from Windows 7 or Windows 8

Open the Control Panel, run Windows Update and make sure the PC is fully up-to-date. If updates fail, run the Windows Update troubleshooter

Use the Media Creation Tool. Do not rely on GWX: go to https://www.microsoft.com/en-us/software-download/windows10, click on Download Tool, save the tool and run it on the PC you want to upgrade. If this did not work when Windows 10 was launched, try again - the tool has been improved.

Ensure that the hardware disable execution (DEP) is enabled in the BIOS, referring to the manual of your motherboard for help if you need it. If you are still experiencing problems, use the Start menu to search for "performance", run the appearance and performance of Windows, click the Data Execution Prevention tab, and enable DEP for all programs and services. Then restart the computer and try again.