Which Anti Virus your used.

avast

norton 360

I use microsoft security essentials. It seems to work well for me, and since it is a windows product it updates with the rest of the windows updates and intergreates with windows nicely. It is also free and doesn't expire.

using norton 360 and PC tools ... the second one is awesome...

nod32 is the best !

clamAV on my Mac. Never found anything :D

Avg

TrustPort Total Protection

ı am using microsoft essentials. it is very good,fast, easy to use

Using Nothing on my Mac except little snitch to block outgoing. On my PC I use MS security essentials which seems to work great and is free (rare for MS).