I use the free version of Avast.
Almost every time I start my computer, it wants me to click the UAC control to allow it to apply an update.
For some reason, it cannot apply any update aside from at start up.
Still, I've had zero issues with viruses/malware and Avast is free.

I run Firefox with Adblock and NoScript.

Have not used AdAware, so cannot comment on that.