I have done some work on some dell laptops, they can be a git to get into, replacing the exhaust fan was fun enough. Graphics are on board and don't expect an AGP Slot 😉, I think that you may be able to upgrade the CPU on some. Memory & HD is easier on laptops than on desktops.
What has driven you towards a latop over a desktop, mobile business use or my favourite, just plain showing off your new toy? 🙂
Corm