Let's try to be a little bit constructive...
Windows (all versions) can't execute on a PowerPC chip - that rules out original Mac G series and more recent. Since the Xbox 360 is built upon a PowerPC chip, Windows XP can't execute natively. The rest of the software may be supported one way or another, but we can't even get there.
Mac OS 9 is PowerPC-centric. Same as above.
Mac OS X could be made to run on such a system, however PPC Macs require a custom Apple BIOS. They won't start on anything else.
Only PPC Linux with a custom bootloader (or a BSD Unix) may be compiled to run on these machines. Once you have those running though, you may want to try running an x86 emulator (such as qemu or VMware) to see if you can install WinXP on this - it will go at a snail's pace, and be very unstable and limited, but it might run.