Clean Win7 install + drivers + basic software = randome little freezes

I have a Asus Zenbook laptop (UX31). I crushed my MBR and somehow I couldn't ever restore it so I did a new clean install (even though I have a Windows.old folder with most if not all of my old files).

And so the usual boring process began: download drivers, installing them, installing the usual software (Avast, Comodo firewall, Chrome, Office, Adobe programs...) and almost on top of that I began doing lot of work with it, sadly I have almost no time to lose.

Somewhere in that process I started noticing some performance problems: doing different things (open a new chrome tab, clicking a link, open folder, clicking low workload buttons in any program) makes the whole thing freeze for 1-4 seconds. Most of the times the mouse can still be moved during the freeze moment, other times even the mouse is freezed for those 1-4 seconds which is more annoying.

In the last install nothing like this happened, system was perfectly fluid. As far as i can remember I have installed the same drivers from the same Asus page, and the same software. Obviously something is different.

I had the suspicion it was COMODO firewall that was freezing things (its alert windows usually freeze more consistently) so I temporarily "disabled it": but problems persist.

Can you help?