Avast! free version runs weekly. Mine is set for Sunday nights at 11:59 pm and shuts off the laptop when finished.
In addition, I use CCleaner, Defraggler to maintain all my computers. I haven't found a free firewall which can handle multiple computers on a home network, so I'm using Windows Defender for Win7. Is there anything better for free?
“When all Americans are treated as equal, no matter who they are or whom they love, we are all more free.” -Pres. Obama
"A great democracy does not make it harder to vote than to buy an assault weapon." -Pres. Clinton