Never install two antivirus on the same device
You never have to install more than one antivirus on the same system.
Anti-virus programs, when they are very powerful, also intercept the activities of other anti-viruses and sometimes interpret them as potentially dangerous. They stop or slow down or have strange behaviours.
For this reason, installing two anti-viruses on the same computer or phone could significantly degrade performance.
If you still want to do so, ask the software vendors for instructions on how to configure the antiviruses in the best way.
Many users, even quite experienced, commit this mistake due to excess of prudence.
Almost certainly in your Windows computer you have already activated Microsoft Security Essentials or Windows Defender, which comes as a windows kit.
If you intend to install a new antivirus, remember to deactivate the one supplied with the operating system.
If your computer is slow when you start it, you may not remember having two active anti-viruses.
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