We've got three computers in our house. The XP machine consistently has problems with Poser 6. It locks up 10 times more often, spits out the memory bug problems on just about every render, and is just annoying. BTW, this machine has 1GB of RAM. My machine is on Win2K. I've had the memory bug one time on one particular render. I've also got just 512MB of memory. My preference is Win2K but I'd say that about 90% of the community only uses XP. In the long run, it is up to you. Our 3rd computer is used primarily for my husband to get on his office's network from home so I'm not even sure what system he has on it. I think he uninstalled Poser from it though.