What's your budget? For Word and Excel? Just about any brand new notebook/netbook you find out there will do Word and Excel fine. You don't need a good amount of ram for that. 1GB is sufficient for Windows XP.
A netbook will do what you want but they don't have a 15inch netbook I think. 10inch is the biggest they get. They have really good battery life and portability is excellent. Price is decent. Great for taking notes, and you can just connect it to an external lcd if you need a bigger screen.