You need the most of everything to run these programs. More is better.
The main things though is the graphics card
The best is--The Nvida Geforce 3 MX (
http://store.apple.com/1-800-MY-APPL....0.5.0.1?58,36 --This is the Mac version, I know there is PC version but don't know where you can find it) can render animations at real-time (Or so they claim). Due to its 76 gigaflop speed.
The next is memory, the more, the faster, the better, and its dirt cheap. I see some places where you can upgrade your Ram to 2 gigs for less the $400.
Processor--I know if you have the right hardware, you can upgrade your processor for about $100 or so, and keep your old processor in there. 3d Max does take advantage of Dual Processors.
Those the three highlights.