Contact HP Support at Contact HP.
http://welcome.hp.com/country/us/en/contact/phone_assist.html#section1On this page you want the 1-800-474-6836 phone number.
Toll free so it doesn't cost you anything, and a 24 hour - 7day a week service.
(Talking to them doesn't cost anything, like it does for some computer support.
I know it's a working number because I called it to verify)
Have the serial number of your computer written down, to give to the nice person on the phone.
This is located in the white Service Tag, on the back of your desktop computer.
The Restoration Disk is free. The shipping and handling is not. $17 for a 5 to 7 day ship, $24 for a 2 to 3 day ship.