Im an IT Technician and to be completely honest I find its all "much for muchness" on my own machine I run Microsoft Security Essentials and have had NO issues at all. I also run a Malware Bytes scan every now and then - (Both pieces are software are free). Majority of clients that come through the store are people that just like to click on everything that says "HEY LOOK AT ME!!!1!!1!!" so with a little vigilance you should be fine!
That's the biggest defence; avoiding dodgy sites in the first place
When I worked for NTL we discovered they had 3 servers used as proxies for some schools.
Windows 2000, not hardened properly, no firewall!
Basically the developers who wanted them didn't want to wait for the build guy at the time to be free, so he gave them the instructions on how to build a hardened server and they only did the bits that looked easy.
I contacted the person who had become responsible for them, told him they really needed to be shut down and rebuilt, either all at once if they could, or one at a time, but he didn't do anything.
Couple of days later El Reg had an article stating one of those servers had tried to infect them with Nimbda
http://www.theregister.co.uk/2001/09/20/nimda_worm_runs_riot/
