I don't think that motherboard should have any difficulty seeing a full 320GB drive. You'll want to be running Windows XP SP2 or Win2k SP4, though.
(edit: or Vista, Vista would see it just fine out of the box.)
It doesn't matter too much which drive you use as your main one, but I like to us a smaller drive for my OS and save my data to a larger hard drive since my data takes up much more space.
Edited by arcman, 20 August 2007 - 02:02 PM.