Running AMD win2k no probs. Only real complaint with P5 so far, aside from not caring for the reg process, is the user manual. I also read the manuals and have always been able to teach myself. Poser 4 manual was not the best, but I could figure it out. I am really disappointed with the P5 manual. I don't need pages and pages and pages of sketchy definition of terms, I need instructions on what to do and how to do it. Duh! Like you know, when you buy something that requires assembly but you don't have any instructions on how to put together, you tend to get a little annoyed!!! Well, consider me annoyed!