You can get the Vipre engine for free with Unthreat AV as it has a decent detection rate. It also uses less than 5mb ram when idle except when updating but the updates are frequent.
Wouldn`t use it just on it`s own though (I run Sandboxie with Spyware Terminator HIPS) but as a "component AV" in a layered security setup I think it`s great.
Good review I`m surprised/disappointed the Vipre HIPS did`nt come into play more as signatures on their own are`nt good enough to totally protect a system these days.
Regards Eck