When you perform a custom installation of Windows Defender beta 2 on x64-based versions of Windows, it does not work correctly.

This behavior occurs because a custom installation of Windows Defender beta 2 on x64-based versions of Windows does not install some files in the correct location.

To workaround this behavior:

1. Start / Run / Control Appwiz.cpl / OK.

2. Select Windows Defender and press Remove.

3. Follow the on-screen removal instructions.

4. Start / Run / CMD / OK.

5. Type MsiExec.exe /x \{A5CC2A09-E9D3-49EC-923D-03874BBD4C2C\} and press Enter.

6. Press Yes.

6. Install Windows Defender using the default settings.