Vasu, do not wory about the current AMD cpu lines and the laptops available. Like ferret has said, both AMD and Intel make reliable cpu. Laptops get hotter than desktops because of small sapce in which everything is fitted.
For your burnt motherboard, you should be covered by warranty as that much heating is not supposed to happen. When a cpu or other motherboard component gets too hot, the computer shuts down or restarts.
can you tell us which particular laptops you are interested in buying. And what features do you require?
you should also take a look at this: http://www.theitdepot.com/laptops.html