You will need to have a boot image (either floppy based or CD/DVD based) that will have access to the missing file, probably on a network file share, and be able to update the disk of the failed machine. There are several diagnostic boot images and processes to build your own available on the web. You can start at http://www.ultimatebootcd.com/ for discussions and examples of how to build your own.
HP does not supply any diagnostic boot images.
The Intel link provided in Alex's reply on this thread is a good source of information, too.