Yes. Running more than one real-time antivirus or antispyware product at the same time can slow the PC, cause instability, and even trigger unexpected restarts. Microsoft recommends not running other antivirus or antispyware products at the same time as Windows Defender.
In this case, Microsoft Defender, McAfee, and Malwarebytes can contribute to the slowdown if more than one of them is providing real-time protection.
To correct it:
- Keep one real-time security product.
- Microsoft recommends uninstalling previous security software when using Microsoft security software.
- If Malwarebytes is only being used as an on-demand scanner, that is different from real-time protection.
- Uninstall the extra antivirus/antispyware apps.
- Go to Start > Settings > Apps.
- Find the unwanted security app.
- Select Uninstall.
- Restart after uninstalling. A reboot is likely needed after each removal.
- Make sure the PC is still protected.
- Before removing other security software, ensure Microsoft Defender Antivirus is enabled and Windows Firewall is turned on.
- This avoids leaving the PC unprotected.
- If an antivirus app does not fully uninstall, use the vendor’s cleanup utility or contact that vendor’s support.
- After removing the extra real-time products, run an on-demand malware check.
- Microsoft recommends the Microsoft Safety Scanner to clean any malware from the PC.
- On-demand scanners such as Microsoft Safety Scanner or Microsoft Defender Offline can be installed alongside real-time security software because they run only when started or scheduled.
- If scans still feel slow:
- Close non-essential apps while scanning.
- Make sure there is enough free disk space, especially on the system drive.
- Restart the PC and run the scan before opening other apps.
If the slowdown started after installing these security products, removing the extra real-time ones is the most direct fix supported here.
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