Server 2003 won't run on that, it has the same interface as winxp + a lot more services running in the background. With 256MB of RAM you can barerly run windows xp so I'm sure server 2k3 won't run very well. As far as MAC OS X Tiger, I don't think you can install that on a PC, you can install PC hardware on a MAC from what I know, the architecture is totally different, but I can be wrong.