. . or you're screwed. The license number on the computer is phony and it won't work (you need to enter the license number on a repair install) - you'll be told you have to activate but activation will be refused. Dell sells the disk for about $98 if you don't have one.
Even if the machine were bootable and you were able to recover the real license number with a program that can do that, you still have to do the repair from a Dell XP disk or it won't work.