I'm looking to buy a system that can run windows XP, has decent horsepower, and also has 12+ comm ports, i'm not looking to slap cards into my system either, any ideas?
See USBtoSerial for a variety of products which will do this. They provide a connector to go from the PC to anywhere from a 4-port to a 16-port external box.
I don't think you'll find a shipping system with 12 RS-232 ports in it. It's just not a requirement that enough people have. If you change your mind and decide you can install cards, look at something like RocketPort. We used those to connect machines in a lab to kernel debuggers and they worked great.
I have found that a good source of industrial-strength connectivity and adapters is B&B Electronics. They sell a variety of adapters, converters, and device servers that can be used for this kind of thing. If the application is testing, you might want isolation, and they sell that too.
A selection of cards to go inside a machine is here.