Re: which notebook
Avoid Alienware notebooks. They are good for nothing but showing off, and they just don't last like other notebooks. They are heavy, have poor quality control, poor battery life, and just aren't practical. WoW should run fine on most integrated graphics cards available on the market today (except maybe VIA graphics).
I would suggest you have him wait just a few weeks until DirectX10 cards start showing up more in notebooks. Then take a look at an HP Pavilion DV6500T series. Currently, all they have is Intel's new X3100 graphics. That should suffice for WoW, but wait a few weeks until you can pick up a model with discrete nVidia graphics (GeForce 8xxx-M series).
I picked up a DV6305US (aka DV6000Z series) last week for about $500 after MIR. Has 128MB integrated GeForce Go 6150 graphics, Turion X2 @ 1.6GHz. 15.4" widescreen. DL DVDRW. QuickPlay. Remote. Not a bad performer amongst other notebooks in its class. I've played Half-Life 2 at native resolution (1280x800 wide), and it played just fine (couldn't do maximum settings though). The notebook finish is surprisingly durable and very scratch resistant.
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