win xp.. 1 gig of mem. athlon xp3000.. very fast.. i use the hair room,face room, firlefly... all work very smooth. never crash.. (sorry only 2 problems will make poser crash.. i just avoid them now...) 1) missing textures. (program goes into some time of loop) 2) changing lights sets... with delting old lights.. it gets stuck sometimes.. besides those 2 issues.. i think p5 is very stable..