I have P5. I was running the Poser program on my C: drive and all my downloads on a 200+ gig external hardrive. It worked okay both with the BUS connection and faster with my new FireWire connection. I just moved the entire Poser 5 program to the external drive a couple of days ago and I have had not problems. If it runs slower than my contually spyware/adware clogged hard drive then it is not appreciably so.