I suggest these: Advanced SystemCare Free and highly recommended by PCWorld, etc.
ESET has a free online scanner. This works quite well as a double check, but can take a couple of hours the first time. Then of course they offer to sell you the continuous-scan package, But I’m happy to use the free version.
Advance SystemCare is useful, but not for viruses. That’s not its primary function, which is to clean and optimize your system. It will find some types of spyware, but that’s pretty much an afterthought, and it doesn’t really deal with infections. Good tool; just not an antivirus.
I usually go to www.download.com and just load the 30 day free trials. There seems to be an endless supply. They also have search options for freeware and shareware.
I used AVG for a while, then switched to Avast when AVG went a bit bloaty at some major version upgrade or other, then I switched back to AVG on one of my machines when Avast kept launching more and more instances of itself, bringing the machine to a grinding halt.
I know a lot of people think the free AV software only does part of the job - and they’re right, but in my experience, so do the paid-for suites.
At work, I helped clean up a case of infection by the Conficker worm - detected by the resident commercial AV program (Sophos), but only after it had managed to infect the machine.
I installed all the latest definitions (it had been a month out of date or so) and a week later, the same worm is back on the machine.
-And I’ve seen pretty much the same thing happen with other AV suites too - including Norton/Symantec (SSSSssssss), McAfeee, F-Secure and others.
Whatever AV solution you use - free or paid - it seems to be possible to get hit by a threat that has been out there long enough to be in the AV definitions, and the first you know about it is your AV package popping up a dialog basically saying “Shit! I let one in”
I like the linked-to closed thread. Since that thread was disparaged for being “zombie” perhaps people will have missed this excellent suggestion there: