Avoid McAfee and Norton like the plague. I personally recommend Kaspersky Internet Security 2013. It's paid but worth it. I've heard that the free version of Avast is also good. As for Kaspersky it does use a bit more resources than other AVs but it's very comprehensive and runs well on mid to high end machines. For something like a netbook go with ESET NOD32, since it's small and fast. Windows Defender isnt too bad either. No matter what you choose, you should consider supplementing your AV with Malwarebytes Anti-Malware and Spybot Search And Destroy.
I used to use the original Kaspersky, initially it was good, but then it failed to find some nasty things. kaspersky TDSSkiller is great, I use that in tandem with Malwarebytes Anti-Rootkit: Because you have to remember that once you get rid of the Virus and Malware Virus Bodies and reg entries, there are ROOTKITS to contend with. I'll use one, then I'll try the other. Malwarebytes anti rootkit takes longer.
There was one year I bought a McAfee licence, which somehow gave me the ability to keep making up new email addresses so I could install it to mroe machines, so I had all my machines protected by it - This was around 2003. In itself the software was not bad, but the state of the PC in 2003, was that there were hundreds of P-IIIs about, maybe even a few 500 mHz Cpus - So running that took about 6 hours even back then.
Now, Norton, maybe back in the 80's and 90's that software actually did something, but when this company called "Symantec" popped up, and started acquiring good software, they gobbled up Norton and wrecked them forever. Now a prime example of this was the AtGuard Firewall, for Windows 98 it was the best and only interactive learning Firewall made for that OS - Then Norton "acquired" it - The company (WRQ, inc) tried to fight it, but were beaten. This did not wreck the company but they did move the old AtGuard forums to a safe place, and they provided AtGuard for FREE during the last stages of the takeover. I still have a copy, somewhere. It just never worked for Windows 2000, I think they even did release a version that could be installed to Windows 2000. This is why I loathe and Despise Norton, and I delete their software on Sight. Well, not Norton Per Se, but Anything with the name Symantec on it. WORTHLESS!
So I've been Using ESET NOD32 for a long time now. However, for Windows 8 I removed it and used Defender. It was good, but I roam areas where I need a little better protection, so I reinstalled NOD32 version 6, and it immediately found a virus embedded in my system that Defender didn't see.
I've tried all other free and paid AV's but nothing does what ESET can do and also be totally automatic. I have a Profile saved I can just reinstall. When ESET finds something, it goes away, that's a fact.
Oh Yah, here is a little note from the develoerp of a part of AtGuard, a part which is still in use by Norton.
Unofficial AtGuard Page