Which two setup systems do you choose?

When you open a Windows 10 installation ISO file, you'll notice there are two setup.exe files—one in the root directory and another in the sources folder (Figure 1). Many users are confused about this. Whether you're doing a fresh system install, adding a dual boot, or upgrading your existing OS, the installer usually runs the setup.exe located in the root directory. This can sometimes lead to issues during the installation process.

1. Fresh Installation Using the Sources Setup.exe

The setup.exe in the root directory only supports upgrade installations and doesn't offer a full new installation option. If you're setting up a new system or installing multiple operating systems, it's better to use the setup.exe from the sources folder. Running this version allows you to choose a custom installation and specify a new system location (Figures 2 and 3).

It’s important to note that if you want to add another Windows system to an existing one—like moving from Windows 7 or 8.1 to Windows 10—you should avoid running the setup.exe in the root directory. Doing so might accidentally overwrite your current system, leaving only the newly installed Windows 10.

Tip: When installing a new version of Windows, follow the on-screen instructions. Windows 10 setup is much simpler than previous versions. One thing to keep in mind: if you don’t have a product key handy, you can skip entering it now and activate it later through the settings menu.

2. Upgrade Installation with Two Setup.exe Options

If you're upgrading your current system, running the setup.exe in the root directory will automatically detect compatible hardware and software, then upgrade your existing Windows version. However, if you run the setup.exe from the sources folder and choose the upgrade option, you can also perform an upgrade. Just be careful—selecting the wrong option could result in a fresh install instead of an upgrade, which may cause unexpected problems for some users.