The problem with the Bryce 5 upgrade serial numbers was infuriating to me as well, so I feel your pain. Corel is a commercial enterprise and should have had the professional wherewithal to make their mistake easier on us consumers. They didn't, but that's the past. I'm running B5 on a MAC with most of my 320MB of real RAM lovingly dedicated to the program. Although I find it a bit more sluggish in rendering comparably set (to B4) files, it's not locked on me. In fact I find the damn thing pretty elegant. My advice in rendering a 264 MB file: take your family on a small vacation. By the time you return, it'll almost be done...