Okay there is no way to get Mac OS X onto a PC.
Yes you are correct that you will need 3 partitions.
1. XP Pro
2. Server 2003
3. Files
As i have stated there is no way to install OS X to a PC. There was a leaked build of a Intel build of OS X taht would somewhat allow for it to be installed but the way to do it is very ahrd. Not many people got it to work. If i remember correctly you also are having trouble installing Server 2003 correctly. If you truly wish to mess with OS X i am sorry to say taht you might not be able to get it done.