I orginally bought a Dell laptop (4 years ago) specifically for using CAD programs.
It was a Dell Intel Core Duo 1.8Ghz, with 2GB Ram with Nvidia Quadro FX 2500 512MB graphics card which had options to change the ' Global Driver Settings' to a specific program, such as Maya, 3D Max, Solidworks and Microstation - but I never found the laptop to be of any use for 3D CAD programs/rendering. Rendering was impossible and navigating in 3D was very very slow.
I'm now looking to replace my old laptop with the new Dell XPS i7 L701X. It comes with a Intel Core i7-740QM (1.73GHz, turbo up to 2.93GHz, 6MB Cache) Quad Core CPU, up to 16MB Ram and a choice of the following graphics cards:
1 GB GDDR5 for ATI FirePro M7820
NVIDIA GeForce GT 445M with 3GB