You don't do them at the same time. You do your setups, then drape and run the sim on each piece of cloth and hair. And yes, it can eat up time doing so. But for animation, it is incredible. As for system resources, 512megs is useable, if slow (hits the swap file a lot); 1 gig is better, and seems to be the first sweet spot when dealing with dynamics. I've done them with and Athlon XP-1700, XP-2500+, and currently with an Athlon 64-3000+. Faster is better, but the older 1700 was able to handle the load quite well.