is there any high quality PCB software that's free for download? I am trying to design a mother board, and want to be sure of the circuitry. Is there any PCB software that if you order your design it takes your design and manufactures it for you? Thanks.
There are many open-source computer/motherboard projects that provide PCB layout output files (called Gerber files) for no cost on their websites. Search for Gerber files specific to the board you are seeking. Example open-source projects include Raspberry Pi, Beagonebone, Beagleboard, and a host of others; Google them.
If you send this set of Gerber files, usually around 8 specific ones out of them, to a PCB manufacturer, they will make the PCB for you. If you need to do this in low quantities (thus reduced cost), you can try a service like BatchPcb or Seeedstudio; there are many others.
You would still need to have the PCB assembled, meaning have the parts/ICs soldered on to the PCB. You can either do this manually yourself if you have a good soldering iron and a hot air gun (although some of the ICs such as in the Raspberry Pi are difficult/impossible to hand-solder), or you can have assembly houses do it for you.
It is indeed true that the Gerber files can be sent out for manufacturing without any editing on your part; HOWEVER, without SOME knowledge of how PCB design/layout works, you would have trouble assembling/soldering the PCB and/or getting it to work. So unless you have professional experience on your side, you may want to start with learning layout for a more basic PCB first and soldering, then jump to this after a few months.
Cadsoft Eagle is a free program for designing PCBs which can output files most pcb manufacturers can use to print your boards.
If you are actually designing a computer motherboard you will likely need the paid version because of the size and layer restrictions. I'd recommend starting with something much, much simpler.
I have completed a number of projects using "PCB". Part of the open source EDA project. See http://pcb.geda-project.org/