I think Windows Defender in Windows 8.1 is very good one for free anti virus.I prefer avast too as best free Antivirus.Is there any problem of using both of them simultaneously?

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    as a general rule, you should only run one active antivirus solution on any given system at any given time. That said, with integrated windows components, usually the big antivirus vendors will detect and ask to disable windows components that collide and replace them with their own solution. Commented Jan 21, 2014 at 7:35

2 Answers 2


From what I have read and have seen, they can peacefully co-exist with each other running with the other in background. I am running MSES with Avast on Win7.


It "may or may not" create a compatibility issue. You might have to turn Window Defender - off.

Computer>C:>Program Files>Windows Defender>>MSASCui>Tools>Options>Uncheck Real-time protection and Automatic Scanning.

Windows Defender in windows 8.1 itself is best and it may not require third-party security programs.

If you install any other Anti-virus in Windows 8.1, It will automatically disable other running external programs in case of a compatibility issue.

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