Best possible Anti-virus program?

Today I bought a windows 7, and I really love it, so I want to take care of it.

Avast was good for my other computer, (Vista). But since Their new update, using License Files. I can’t find a key for the pro one anymore, but is the basic, free program good enough?

Or Is their another good program?

AVG Last time, on my vista it didn’t update or scan shit!!!!

so anything else thats good for me?