the way those downloads have unfettered access to your hard drive etc better hope that you have really robust AV
even then if you have some free AV that doesn't run unless you run a scan manually,
well why not buy legitimate or proven apps?
The freeware isn't always a dog,
but 90% probably is.
I just wouldn't chance anything beyond spybot or malwarebytes
just asking for it...
In the many serious tests I have seen NO single av software identifies every hazard every time. As for the free/paid comparison, in the last evaluation of products in both paid and free categories which I read, the free version of "Avast", the Czech av application, came out with the highest score - as it has in some previous tests. There is also a paid version which includes a firewall and additional functionality which some may wish to have. I have never
seen either Norton or McAffee, the most commonly pre-installed security applications, come first in these comparisons.
I have used, installed (and removed) many different security applications over many years in combination with a free third party firewall and Avast is by far the best, particularly in the newly revised version which has an excellent interface including the capacity to automatically identify and update out of date software (Flash, Java etc) which contains vulnerabilities. It incorporates a scheduled boot-time scan function. I have no connection with Avast except as a very satisfied, malware-free, user. The other widely used free application, AVG, in my experience, is terrible. Someone I know who maintains PCs commercially told me that the majority of malware-ridden PCs he encounters are likely to have AVG installed.
I regard the practice of supplying PCs with three-month evaluation copies of paid security software such as "Norton" (it used to be McAffee, but that seems to have dropped below the radar except in Central America...) as close to being legitimised malware since it blackmails the user into paying for something which he hasn't ordered - and doesn't usually understand. I've lost count of the number of people from whose computers I have removed hugely out-of date versions of these programs which they fondly believed were still protecting them in some way.
From what I've read and seen, a high proportion of the malware about nowadays evades security by the simple expedient of fooling people into installing apparently innocuous software which also includes unwanted and potentially dangerous components - as appears to be the case in the OP. I never use the "quick install" option for anything;"custom install" usually reveals preselected cr@pware such as unwanted browser plugins.
At least as important as the software is the users' understanding of what to avoid. This is a much bigger problem to address.
As for "Spybot", that's never been a serious security solution as far as I recall. Unless it has been totally revised it was only ever only good for removing tracking cookies etc.