Get F-Secure Internet Security.
F-Secure uses Kaspersky, Hydra, DeepGuard 2.0 and Blacklight to keep your computer clean(So you basically get 5 antivirus / antiadware-programs in one.).
And it may sound like it hogs alot of CPU, but actually, it doesnt, because it kicks the needed "engines" in when it finds a threat.
It also keeps your computer clean from spyware, and can detect if someone is hacking you.