My maintenance routine is, every Monday morning after turning on the computer run the built in Disk Cleanup, run a quick scan with MalwareBytes, although I have the Pro version which is running all the time, then a quick scan with SuperAntiSpyware, the free version, task scheduler is set to run a Defrag every Monday night and Microsoft Security Essentials is set to do a quick scan every night.
I also have SpywareBlaster quietly doing it's thing in the background and I get all updates that are needed through Windows Update.
Acronis is set to do an image every Friday and I use the built in firewall plus I'm behind a very strongly set up router which has a firewall.
I think that's it.