Hi,
Comodo firewall is extremely light.It is running at around 4000k ram here.
Also i would like to add the so-called problem with comodo firewall and avast webshield does NOT exist when i used them.
To be perfectly honest why on earth would you wish to be blocking anything on your computer…the suggestion is preposterous.
If you do not trust any connections from any installed programs then why have it installed at all…!

I tried to get outpost firewall installed but upon the reboot my laptop went into a never ending crashloop and this was after several attempts.
Privatefirewall is another hit and miss installation procedure which if it goes haywire then it causes no end of mischief.Plus the GUI is plain rubbish and looks like it belongs on a zx spectrum.

Yes for lightness the comodo and windows firewall take some beating and comodo is rich with its settings and customizations and as i said before i never experienced any issues when running with avast.
I highly recommend it.

Thank You.