AutoCAD models?

I was wondering if there was a place where i could get some AutoCAD models, like case fans 80-120mm because i'm currently doing a small project, my first, with CAD which is to make a vent from an 80mm fan to the opening of ATI's large dual slot GPU cooler with the "Centriphical fan" (probably just a blower).
I'd like this since i'm not very adept in cad, and it would help me alot
-thanx
Prince