I simply second this link I saw:
It is so true, there is so much crapware on new PCs. OEMs create crazy named power schemes, and all sorts of gimmicky applications. It is just insane. The bundled anti-virus other security software slows the PC to a fraction of its true performance, but of course I can not recommend disabling the real-time scanning as that would put you at risk. I can say that I don't use any real-time scanning.
As for which security software I use, I'm giving the FREE Microsoft Security Essentials my recommendation. Why? You know they did it right as far as achieving minimal impact on performance. I hate to see Microsoft wipe out whole market, as they've done in the past, but they seem to have done a decent job with this product and it is completely free.
Anyway, as for new PCs -- Yea, do any non-techie recipient a favor and clean them up, like BestBuy offers to do for however much. Funny that a big retailer even charges to clean the OEM crap off the PC at purchase, when you think about it.