Manually run a one time Windows defender scan with Mcafee being the exisitng security softwarr

Windows Defender Antivirus and McAfee should not both provide real-time protection at the same time, but it is possible to use Microsoft’s on-demand scanners for a one-time check.

Because McAfee is the existing real-time security software, use one of Microsoft’s on-demand tools instead of trying to re-enable full Defender AV alongside McAfee:

1. Use Microsoft Defender Offline (on-demand, one-time scan)
   Microsoft Defender Offline is designed to run a one-time scan outside the normal Windows environment and can coexist with other real-time AV:
   • Save all open files and close running programs.
   • Open the Windows Security app (search for "Windows Security" from Start).
   • Go to Virus & threat protection → Scan options.
   • Select Microsoft Defender Offline scan and then Scan now.
   • Confirm the prompts; Windows will sign out and restart.
   • The offline scan runs (about 15 minutes) and then Windows restarts normally.
2. Use Microsoft Safety Scanner (also on-demand)
   Microsoft’s guidance recommends using on-demand scanners like Microsoft Safety Scanner or Microsoft Defender Offline alongside other real-time products. Safety Scanner is a separate download that runs a one-time malware scan without replacing McAfee’s real-time protection.
3. Avoid running two real-time AV products together
   Microsoft recommends not running Windows Defender real-time protection at the same time as another antivirus or antispyware product. Multiple real-time engines can cause performance issues and update/install errors. Keep McAfee as the real-time product and use Microsoft’s scanners only on-demand.

References:

• Run and review the results of a Microsoft Defender Offline scan
• Antivirus and antimalware software: FAQ