First line of defense for me is AVG 9 and my firewall. Since I use the Firefox browser I use a plug-in called AD Block Plus which blocs ALOT of adds and pop ups out there. Plus I can easily add my own filters for blocking some adds that do get threw. If my system does get infected AVG is good at detecting it and if it doesn't get rid of it I have a few programs that will, such as kill the process of the infection and I can actually erase anything from my hard drive at to just 'deleting' it. It takes some time getting rid of an infection but I am pretty thorough about it.
