I really like Microsoft Security Essentials 2.0. It doesn't have many options, but it did receive a VB100 Award from Virus Bulletin (meaning it didn't let any sample zero-day or wild-list viruses pass and execute). It also monitors Windows Firewall, so there's only one program needed to monitor both (you will have to open the firewall to make changes, but MSE2.0 will let you know it's A-O.K.). You can make your own schedule, but you cannot configure it to do quick scans on one day and full scans on another. That shouldn't be a problem as quick scan is recommended most of the time. Another downside is that you cannot pause a scan, you can only cancel it. That being said, it is still an excellent free anti-virus.
As someone else said above, I'd use MSE2.0 in conjunction with Malwarebytes. Other security programs I would suggest would be Secunia PSI (free!). It looks for un-patched software that could potentially compromise your system; if possible it also finds websites you can patch them.
I got this program after reading an article in MaximumPC: BufferZone Pro (free!).
"It works it's mojo by isolating all web-based activities in a virtual bubble." (MaximumPC). Basically, if anything goes wrong and you get an infected file, it gets written to a virtual folder. This is normally more preferred to enthusiast instead of Virtualizing their entire OS (of course Virtual Machines will always be the most safeguarded. If you get infected, nuke the VM and start from scratch!).
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