re AVAST which in the past I reco'd and no longer do so....
Just worked again on a gorgeous hp dv7, i7 with dedicated radeon gpu... just a killer system.
this is the second time I've had this one in my shop in 2 months - the last time I completely clean installed win7 to get rid of malevolence. Came back, and was reinfected with 'my search' search.conduit and relateds, variant "n"... they keep morphing this one. lots of hangers-on...
Paid "pro" edition of AVAST had been up and running the whole time [the lady insists it does some good]. never caught any of it. I doubt seriously that any other "AV Suite" that eats your resources would have caught these either. I got paid, but it was a nuisance having to fool with it.
the lady had uninstalled [without asking me] WinPatrol - "because its interrupting me too much" !!

duhh...
so it goes in pc land
i reinstalled WinPatrol told her she's "on her own" again regards the faux "security" of AV suites, explained to her how to respond to WinPatrol's "interruptions" and, once again, a warning or three about toolbars, "shopping sites", and "registry fix"...etc du jour "click me to solve your problems" links, et al. I doubt.....
anyone that does what I do knows that there are literally countless good, potentially potent PC's out there all around us that are effectively out of commission due to the swarm of grayware, malware, adware, popup-a-million-ware, choked browsers, rredirects, etc, so people eventually just move on to iphones, ipads,'droids, etc and quit trying to do any useful work on PC's.
as an aside, AVAST on android is a total disaster. can literally destroy your handset by overheating unless caught early and vanquished. The 'droid community thankfully has figured out that just a little periodic maintenance with a couple of good tools is FAR better than loading ANYthing realtime in the background
imo M'soft has lost the small-device war, and is in grave danger of losing the "touch device" battle altogether, permanently becoming a niche player. 'tis a shame because there is a lot of good utility in a Win 10 PC - it can be the hub of everything if properly done