Norton is definitely the one to use as it`s the only one that seems to get the real awkward little buggers that don`t do a great deal of damage but just slow everything up,and if you are on broadband it automatically updates real quick,so well worth the subscription.
Also worth getting is adaware(version 6 i think),it is freeware and finds and removes all of the spyware that invisibly infects your pc(i ran a diagnostic on a mates pc recently and he was infected with 1700+ spyware programs !!!!!!!)

If you want any more info give me a shout on pm or e-mail m8.

Cheers.........Rob