What antivirus pogram do you use?
I use Microsoft Security Essentials, because it’s free and doesn’t use a bunch of system resources. It uses the same scanning engine as Microsoft Forefront.
I have heard that a lot of people like Avast. It’s also a free antivirus program.
If you want a good program that can supplement your existing antivirus solution, you should take a look at Malwarebytes. Malwarebytes is a free tool (with a paid pro version available) that does a really good job at finding rogue antivirus programs and other spyware.
I use AVG. I haven’t had anything worse than tracking cookies in the 5 years I’ve used it, although I’m not sure if that’s my antivirus or if I’m just a cautious clicker. Regardless, it’s relatively lightweight and painless. It has bloated out in the last couple years, but it’s still tolerable.
I also run Spybot Search and Destroy (safer-networking.org) every now and then. No live monitoring that I’m aware of, but it’s good at getting rid of spyware if you think you’re infected.
Security Essentials is free too. I haven’t been to happy with AVG lately.