The Simple MobileÂ® logo and the Simple MobileÂ® product images are registered trademarks of Simple MobileÂ®. PINZOO is in no way affiliated with Simple MobileÂ® or any other entity for which a logo or name may be present.
1 Click Tools at the top of the Windows Defender Window. 2  Click Options in the Settings section of Windows Defender. 3  Click Default actions.  Set the default actions (recommended action based on definitions, Remove, or Quarantine) for each level of alert and then click Save.
Open Settings tab and click Real-time protection on the left. Make sure there is a check mark in the Turn on real-time protection (recommended) check box. That's how you activate or enable Windows Defender in Windows 8 and 8.1 after uninstalling some competing free or paid anti-virus product.