I could do a full guide on setting up a Linux server for home/personal use (file shares, media server etc.). Just PM or write a comment if you are interested.
Check out clonezilla :) I think it will be able to solve your problem. But stay away from the "dd" command that 'chris' suggested if you aren't familiar with linux.
You can install OSX on a PC, you will most likely just run into driver issues. If you are building a new PC you could do some searches and find out what hardware is compatible and then buy that platform.
I would recommend Ubuntu server if you want an complete vanilla OS. But remember there are also releases of Ubuntu with other desktop interfaces, ex. Kubuntu = KDE, Xubuntu = XFCE etc.
I would not recommend spending 500-600$ on a system that only is going to do something a 35£ raspberry PI or 200$ atom machine could do flawlessly :)
My recommendation is XBMC :) Always go open-source when you can :)
Are you connected to the router? It seams a bit like you don't have your network setup correctly.
You say that you get your external IP when running "ipconfig" in CMD, that suggests you have no router connected before your PC.