Installing more than one program to constantly scan and monitor your PC for viruses and other security threats can create problems, because the two applications will likely interfere with each other’s work. Clashing antivirus programs can cause the computer to behave erratically and run more slowly as the applications battle for system resources.

Microsoft advises against running its Windows Defender security software on the same system with another installed third-party antivirus program. Likewise, antivirus software companies also warn against using other system security products when you are using theirs; Bitdefender, Kaspersky Lab and Symantec all have articles on their sites explaining the potential problems in detail. Programs that do not constantly patrol your operating system, like mail scanners, may not be an issue.

When you install a third-party antivirus application on a Windows 10 computer, the Windows Defender Antivirus software should automatically turn itself off and make way for the new program to take over. Some security apps may also include a firewall feature to block online intrusions, but Microsoft’s own Windows Firewall should be used if the antivirus app does not offer that protection.

To see the software that is protecting your PC, go to the search box next to the Start menu and enter “Control Panel.” Select Control Panel from the results list and under “System and Security” on the next screen, choose “Review your computer’s status.” On the next screen, select Security to see a list of programs at work.