I am trying to get my Dads laptop with windows xp on it back up and running
You don't mention how the laptop came to be in this state but it sounds like either a bad hard drive, some missing or corrupt boot files or possibly a malware infection.
In any case without installation media or at least the recovery console installed you may be out of luck. Bassfisher's idea of borrowing from a friend or neighbor may very well be your best bet. XP was a bit finicky about product keys matching the media with respect to OEM vs. Retail so you'll need that to be correct as well as Home vs. Pro vs. Media Center Edition.
If it came pre-installed than perhaps there may be a recovery partition which you may be able to access with a key...