I don't even use security software.
It is for the birds.
Honestly, I have never had a computer runnign faste rthan my Dual Core with 4 GB of ram and no AntiVirus, no AntiSpware or anything
Solution:
I don't use IE and know what all my running processes are.
I use TCPVIew on occaseion to make sure nothing suspicious is running.
I have my registry, group policy, and ntfs permissions locked down well enough and don't login as administrator except when I want to install something.
I use partimage for imaging.
As for my tools, partimage, sometimes a windows disc, and a can of spray air every month on the air filters and inside ever 3 to 4 months.