Go to HPs Web site, put in your model number, and search for recovery discs. You should be able to order them online. If all that fails, call support, and ask them to give you the exact link to your model, so you can purchase the recovery discs.
Note: The recovery disc has your OS on it. A recovery disc is like an image of the computer the day it was purchased- put's everything back how it was without the hassel of installing drivers, software, etc. Very useful- if you never install anything else- Back your data up! Always!