If the computer is 1yr old -> norton or mcafee

If older try NOD32 or kaspersky (2-3yrs)

Dont bother with trend micro, bit defender or f-secure. Resource hog and not all that effective.

CA is good. 80% as effective as Kaspersky with low system resource utilization beats Avira, bitdefender or trend in real life.

Cheers
Xyned
Tech support specialist Bigpond Adsl, Hsdpa, Cable and Security