I don't have access to a USB keyboard and I can't believe that one is required to install Windows 2000. I'm getting no error messages, the three lights on the keyboard flash and then go out when the GUI pops up.
A USB keyboard isn't required to install Win2K, but if your ps2 port is having issues, then it can be narrowed down by using a USB keyboard.
Again, more hardware details (motherboard, etc) would be helpful.
~Ladi