Just because it's for a 10 year old does not mean you want to get the cheapest thing possible. I would recommend getting him the cheapest computer with a dual core processor and a cd drive.
I have seen a scenario play out more than once:
The parents get the kid a netbook, the kid loves it for a bit. Once the fun where's off, he starts to realize it's quite slow and just puts it with his other forgotten toys. Same thing with the dual core
Smaller children tend to be very impatient, especially when it comes to computers (hell, even adults get super impatient on computers). A dual core won't cost you much more, in fact when I was still in retail, I remember seeing a few week specials on 329.99 and 349.99 toshibas that had dual cores. They had decent build quality, only 2gb of ram, but hey it gets the job done.