RedXray & StangFan - Excellent advice! My tiny little job in retirement, is cleaning infections, & computer repair.
Buy a pick up truck or let it be known you fix computers, & wow you become very popular.
All AV's have a place in "settings" where you can exclude, stuff you know to be safe.
Kaspersky KAV or KIS (kaspersky anti virus, or kaspersky internet security), is the 'gold standard' year after year, by a good margin, so say's, multiple testing orgs. It's a little pricey!
Keep in mind free software AV's (bitdefender, avast, etc) offer free versions, as an inducement, so you will purchase later. The free version have to be great, or you will never pay for the paid version.
I recommend to all my client(s) who wish to go the free route 360safe. c.o.m. Product 360 Total Security, (free excellent phone protection product as well). It's always free, the strategy, is give the product away, then, the happy camper will mention it at work, then charge corporate clients.
360Total offers just some features, analyze optimize startup, you can easily knock 10 - 30 seconds off booting process
They license the Avira & Bitdefender AV engines, cloud scanning & a proprietary AV engine, all in one package.
It runs very lite!!!
Free sandbox no malware can survive, a sandbox.
Free browser protection
Free superior FW
It will patch (apply updates) to your software.
It's like going to the county fair (It slices, it dices & even walks the dog), but it works.
It's from China, but whats not anymore.
ALWAYS ALWAYS go on line DOWNLOAD your candidate for replacement AV, then go "OFF LINE", then "UNINSTALL" your old AV, then install the new AV. U don't want to go online without an AV & you don't want two AV's fighting each other.