for CAD and multimedia U better not get a Laptop, cos it will be low on performance, better go for a Desktop PC with dual core CPU, that would be the best choice
However, if u are keen to go for laptop, I would suggest a customised dell inspiron 9400, but that may go beyond your budget, but its' 17" LCD based
else u can go for inspiron 6000
core duo cpu will be best suited, add to it a DirectX 9c based graphics card, since it's CAD, nvidia geforce 6 series is prefered, cos it has better openGL 2.0 performance, for Premiere pro 2.0 or Autocad or Viz
Get 1 GB RAM for sure, & not to forget a Mouse, cos the touchpad sux big time for CAD, the Harddisk size as required