Serial ports

Here is a question for my fellow computer junkies:

I have multiple dell machines kublai, mummies, sleestaks, etc. (code names). I am running into a problem on most of them. Serial port(s) not working. I have had dell replace all of my motherboards, reinstall windows from scratch, debug command shows prots are running, uninstalled ports reinstalled, but still no go. I know it is not a software issue, and i know its not the dell parts (i work for them, and i pretty much chose the mbs). How cani fix the computers so i can use the ports? And no i am not joining the usb or usb2 rush.