I was having the same problem and I tried a shot gun approach, since I couldn't find a solution, and I got it to work! Basically, I put the WindowsXP Pro. cd in the computer and restarted the comptuer. I proceeded with the "normal" installation of the OS and at one point I selected to "reinstall" or "restore" of the OS, I selected "R". Somewhere along the way it asked for the administrator's password. It continued as it did the very first time it was installed, but it just fixed the system and started the devices. I rebooted at the end of the installation and entered one of the user accounts and everything is working fine.
Just to be on the safe side, I backed up all my critical data prior to doing anything.