When you start up Asset not found for the first time, Windows Defender is on and working to protect your PC by scanning for malicious software.
Windows Defender uses real-time protection to scan everything you download or run on your PC. Turn off real-time protection temporarily by selecting the Start button and then selecting Update & security > Windows Defender.
If you have Asset not found, you can't get Microsoft Security Essentials. But you don't need it because you already have Windows Defender, which provides the same level of protection. Windows Defender will turn itself off if you install another antivirus app.
Windows Update downloads updates for Windows Defender automatically to help keep your PC safe and protect it from attacks.
Windows Defender regularly scans your PC to help keep it safe. If you want to set your own scan schedule:
To turn off real-time protection, follow steps 1 through 3, and then clear the Use real-time protection (recommended) check box.
Article ID: 17464 - Last Review: Apr 27, 2016 - Revision: 18