http://shop.lenovo.com/us/notebooks/.../l-series/l420
Watch the "View ThinkPad L420/L520 tour" video at the bottom in the related resources section. They talk about the milspec durability testing, which should interest you. I worked with these laptops for 3 years (I was a desktop engineer), which is why I ended up with one as my own personal computer. They are great machines.