Why won't my keyboard work on my PC?

I have a custom built PC that recently the motherboard fried on it. My friend put in a new motherboard and got it up and running for me but now the USB keyboard won't work. I also tried a PS2 keyboard and still got nothing. I have my PC pword protected and can't type in the pword to log-on. I have an illuminated keyboard and it lights up when the computer is on but I just can't type anything. Any ideas??