Can I install two or multi antivirus in one computer

Not if you want either to work right. They tend to conflict with each other when you do that. Pick one or the other, but use only one.

Listen to smoothy...

I get clients literally everyday complaining about there brand new computers that are incredibly slow.

7 out of 10 times that have bought and installed an antivirus but forgot about the trial anti viruses that are factory loaded.

If you have a windows 7, then your fine... add an antivirus software to your computer and if that runs out your computer has a backup plan.. but I recommend a free one.. but you will have to update it occasionally

if u have a windows 7, then ur fine...add an antivirus software to ur computer and if that runs out ur computer has a backup plan..but i reccomend a free one..but u will have to update it occasionally

What does WIndows 7 have to do with it?. you can't run two of them under Win 7 any more than you could under Win XP or any others.

More than one and they WILL be fighting anoung themselves up to and including the point the machine stops working altogether as a result.

And the free ones while better than nothing at all... aren't as good as a full featured program. And not all Anti-virus programs are equal. Like anything else there are always the good ones and the bad ones...

And some of those that parade around as free Anti-virus are actually nothing but Malware programs... very, very nasty ones.