a tough one, uh :)

well, let us konw if you want fight with it or reinstall everything. The latter usually is faster and cleaner :)

just as i said before, a "well" written virus can activate itself in many ways. since you've mentioned registry and you still want to have fun:(, try RegMon. It monitors all registry activities and you'll find out who's puting that registry entry back in again. setup a filter first or you'll have too much data.