i have an athlon 64 3400 with windows xp pro. i did have problems with crashes but recently had to returm my computer to have the motherboard changed from an MSI to an ABIT MOTHERBOARD.i do not know whether this will solve the problems i had with Poser or not (i just got the PC back yesterday )when it was working right my renders were super fast ,what took 13 minutes on my old pc took 78 seconds on the new one.if you are considering an athlon 64 ,i would suggest asking the company how much testing has been done on the processer with the particular motherboard they are offering. i hope my problems are over.