Article ID: 925559 - View products that this article applies to.
When you install Microsoft Windows Defender on a computer where Microsoft Windows Antispyware (Beta) is also installed, neither product runs correctly.
This problem occurs because Setup installs Windows Defender files in the same folder where Windows Antispyware (Beta) files are already installed.
To resolve this problem, uninstall Windows Antispyware (Beta) before you install Windows Defender.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.