Unresponsive Keyboard During Clean Install

I have an interesting problem. I bought this computer five years ago. It is a Micron Millenia EX PIII, 733 MHz. It was originally designed to run Windows 98. Whenever I try to perform a clean install of any other version of Windows besides 98, my keyboard becomes unresponsive and I cannot select the appropriate items to continue with the clean install. For example, if I put the Windows XP cd into my system and restart, I will boot from the cd. The cd will then load setup files and go to a screen that asks if I want to continue to install Windows XP; then I'm supposed to hit ENTER. However, my keyboard is completely unresponsive and the computer will accept no inputs from it. I can't even change the caps lock or num lock settings. This occurs with Windows 2000 as well. I can perform a clean install of Windows 98, however, probably because the entire sequence is automated and I don't have to make selections until the main components of the OS are loaded on and Win98 is already running from my HD. This is a really fustrating problem because I want to do a clean install of Windows XP but I never can. I always just upgrading over 98. I have also tried another keyboard that was functional on a different computer when performing a Windows XP/2000 clean install. When I plugged this new keyboard into my system, it too became unresponsive during the setup screen. My keyboard is a Microsoft Natural Keyboard and is PS/2. I'm sorry for the length of this post, but I'm really desperate. I've been trying to figure this out for five years now! Any help would be greatly appreciated. Thank you in advance, James.