Per Red Cloud:

I don't use anti-virus thing it's slow down the speed. I rather
reinstall OS again.

Try Avast. I'm a borderline lunatic when it comes to response
time and find Avast tb no problem on my regular PC.

On my netbook, it gets in the way a little when the device is
first booted as it downloads the latest updates - and taxes the
pitiful little Atom processor. But even I can live with that.

As far as running bare goes, what about the time between your PC
getting infected with malware and your discovering the infection?

Lotta Bad Things can be done by the malware perpetrators during
that time. Your address book can be harvested, making you a PITA
to anybody unfortunate enough to be in it. Keystroke monitors
can harvest your UserIDs/Passwords... and so-on...
--
Pete Cresswell