I have just downloaded the AVG Security Suite on a months trial and was impressed with it. They say Nod32[esset] is the best I suppose look around and see where you can get them the cheapest.I believe Kaspersky is still free if you have a Barclay's account.
I use this click here I know that many rate Kaspersky highly. Im running three PCs with two people that are not very PC literate and hence happy to with three user license. Very happy with the regular updates every two or so hours,together with online backup and first rate support on the odd occasion I needed it. But each to their own.