Hello markd359,
If the laptop is from a major manufacturer, it's likely it came with Recovery or Reinstallation disc(s). Generally speaking, if you use these to run a full recovery or clean installation, it is not necessary to input a product key. Please check at the support site for your laptop to make sure that this is true in your case.
Please run this utility and copy/paste the results into a reply:
http://go.microsoft.com/fwlink/?linkid=52012
For great advice on all topics XP, visit http://www.annoyances.org/exec/forum/winxp