You will notice that P5 asks for a .bum file it can't find if you installed items that have a .jpg as bump map and the creator assumes that the user converts it to a .bum. Just change the pointer in the file in question or (if you are lazy like me) point to the correct file when the problem accurs. I suppose that P5 can theoretically use a .bum file if you load it in the bump channel, but you are supposed to use .jpg's as bump maps. Saves you a lot of hard disk space as well! Watch out for certain MAT-files, they might not load bump and transparency maps correctly in the Material Room. I developed a habit of always checking if maps got loaded correctly when starting to use P5, made me spot the most obvious problems and correct them. The problem with transparency settings loading incorrectly was a big issue, but it was resolved with the service packs. I have heard problems with light sets from P4 creating problems in P5, but I have yet to experience it (maybe because I seldom use light sets, I think it's fun to create my own lighting!)