
However, it may qualify if you upgraded to a later Windows version.
Windows XP or Windows Vista Your (probably very old) PC is not automatically eligible for a free Windows 10 upgrade. (See the following section for a definition of what that is.) You have to install a "qualifying license" first. This is also true if you are running the Windows 10 preview in a VM. No operating system If you built the PC or bought it without a qualifying copy of Windows, you are not automatically eligible for a free upgrade, even if you are currently running the Windows 10 preview. Windows 8.1 You can upgrade to Windows 10 from Windows Update. After that's complete, you're eligible for the free Windows 10 upgrade. Windows 8 You must first upgrade to Windows 8.1 (free in the Windows Store) and then install the free Windows 8.1 Update from Windows Update.
But all PCs sold with Windows 7, even pre-SP1, qualify for the upgrade.
Windows 7 Service Pack 1 is required before you can upgrade using Windows Update.