I think things are becoming complicated..
I'd be using ANSYS, ADAMS, UG NX & CATIA.
Let me help myself with the choices....
CPU : Q6600 or E....?
M/B : P35, which one?
RAM : 2GB @800 GHz, which one?
HDD : Seagate 500GB or WD 640GB or ..?
DVD-RW : ....?
PSU : VX450 or ..?
Cabinet : any VFM ...