Norton Internet Security 2006. I purchased it in December and am extremely pleased with it. Alot of people on here will say it is a resource eater but definitely not in my case with a Pentium D and surely not in yours either with Amd Athlon 64 x2 4800. People will also say that it makes your system crash but in my experience mine hasn't crashed once.
Pc World are selling NIS 2006 + Norton Go back for £24.99