As for CAD & CAM,
An Intel P4 3.0 Ghz + or equivalent AMD Processor.
512 MB RAM min, 1 GB + will do better.
A 120 GB HDD with min 7200 RPM,
Nvidia Quadro Series GPU or equivalent ,
A 17" FLAT type CRT or LCD Monitor. Here higher the monitor size better the viewing & working experience.
Windows 2000 Pro or Windows XP Pro.