The keyboard function has been embedded in the motherboard for all personal computers made in the last 20 years and if there is a non-USB peripheral card you could use, I've never seen it. I'm not sure that a USB card would work and, in any event, a replacement motherboard would be cheaper than a USB card and USB motherboard.
I see a couple of keyboard port failures a year so it's not unheard of. But before you consign your motherboard to the scrap heap, you might check for a keyboard lockjumper and make sure that the keyboard port is not disabled by either a switch or a jumper.
Also the usual troubleshooting of swapping with a known good keyboard (although it sounds like you've done that) and, if you really get to the point of having nothing to lose, clear the CMOS and reboot. Twice I've seen that bring a keyboard port back to life so it might be worth a try.
And one final thing to try - if you can remove the motherboard from the case, take a good look at the base of thekeyboard connector from the bottom. Often, the solder joints get broken by repeated wiggling of the keyboard connector and a quick touch with a soldering iron brings it back to life. These are multi-layer motherboards so it doesn't always work butmore often than not, it does.
paul
