Any new computer you buy will be able to run WoW (possibly netbooks aside).

I'm currently running a Compaq Presario V3000. Not bad specs, fairly cheap, looks nicer than a macbook.

Also Compaq/HP have a really good repairs policy. I called them about this laptop when it was six months over warranty and they sent a courier to pick it up the next day and replaced the motherboard. All for free.