I have to agree with everyone who says upgrade your OS. But I also have to admit, I have a machine with 98SE and everything works fine, including Poser 4. I also have to tell you the machine on which I'm running Poser 5 has XP Pro and I suffer from frequent freezes, too (only with P5, that is). So the OS change may not help. But you should do it anyway...it won't hurt.