I used many Antivirus programs like McAfee,Norton and now Kaspersky Internet security.According to my personal experience all these Antivirus slow down the computer.because all antivirus System Memory.
McAfee slow downs the system startup,because it directly sits on the RAM and checks all the programs.It's very good Antivirus.McAfee is the different type of Antivirus.In Antivirus there is some types,find it in Google search.
Norton also done the same thing and does not help me a lot.
Kaspersky is entirely good for Windows 7 only in start up.If you scan your system using the Full scan option by Kaspersky.The system is very slow.One good thing is it protecting me online threats like phishing and Adwares and other malwares.I prefer to use McAfee but it's costly.
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