I have an old (unknown date of build) computer that once upon a time was a server. It has a Asus SK8N mobo. I dumped a spare hdd into it and proceeded to try to install XP PRO. For some unknown reason at the POINT in the setup to start the install it will not accept input from the keyboard. Hitting Enter at Press any key to boot from cd works, setup starts and proceeds . At the point where it prompts to hit Enter to install Windows it will go no further. Normally the first light (next to Caps Lock) comes on, this is not happening. So, I figured I'd pop the CMOS battery and leave it out for at least 10 minutes. Upon putting the battery back in and firing it up it tells me BIOS is not installed. HMMMMM, K. Fire it back up again, this time hitting the Delete key. Viola .... I can access the BIOS. Make sure nothing (as far as I know) is awry. Still same result from here on out.IMO it is not a BIOS issues. I think you have some hardwarenot working well.
Here are some suggestions. This is more based on experience than on any theoretical ideas. From my own experience Windows XP will fail uninstallation for any number of hardware related issues. It does not always indicate what the problem is. The fact that the keyboard is not responding does not mean the problem is the keyboard. It can be a separate issue.
Need to verify that the keyboard really is okay. The fact that it works in the BIOS does not prove the keyboard is perfect. Also, you need to make certain the hard drive is in good condition and USABLE by XP. If possible, try formatting that hard drive with another computer. Just make sure that it is in good condition. Also check the amount of RAM you have installed. Windows XP may fail if there is anything wrong with  RAM. Again, don't expect it to give you a meaningful error message.
And don't forget, the CD reader also has to be in good condition. It has dust in it,  XP may fail to finish the installation.
Best I can  offer.  Thank you. I have verified that both keyboards work on a known good computer (they are sitting side by side and I switch back and forth, I'm on my good one now). One keyboard is USB the other PS2 It was working, running Windows 7 prior to this. I RAN DBAN on the hard drive and it passed. I have blown out all dust in every nook and cranny and unplugged and reseated all the cables. I wanted to load XP because it just wasn't quite up to par running W7.I forgot to mention. Depending on BIOS,  XP might not instal if it has SATA drives.
That is a BIOS option.I'm using a IDE drive.