I tried Kaspersky out, it absolutely was not lighter in use than Norton was. The problem was that it would scan incessantly and I couldn't change it's behavior. While scanning, it slowed the system (dual core 2.13 running at 3.2Ghz, 2GB ram, 10k RPM HDD, NOT slow) noticably and hammered the hard drive. It did seem to be a better virus engine though, if I could've sorted the issues out i would still use it. I went back to Norton Corporate. Still looking at other options.