Whats an antivirus that isn't too overprotective?

Hey every1. I want a antivirus that has a high detection rate, isnt too much of a memory hog, and that doesnt pop up and freak out of a file OR locks down youre computer. I tried kaspersky 2009 trial and it was excellent but many people say that it locks up youre system and the reply to that is to just change its settings. So what do you guys think? Thanks