No offense, but your friend has no idea what he's doing if he downloaded eight anti-virus programs. Any more than one is going to hurt your performance and possibly system stability.Is Microsoft Security Essentials free? Or does it cost money?
@My friend downloaded 8 different Virus Protection and his computer runs really fast.
I recommend Microsoft Security Essentials, which is free. If you have money to spare, ESET NOD32 is also very good.