If it's a newer Hewlett Packard or eMachine (and maybe Compaq), the data needed to restore to factory settings are on a hidden partition on the harddrive.
While the machine is booting up, read each screen. On HP's, you should get a screen telling you to press the F10 key. eMachine is similar, although I can't remember which key it tells you to use.
Both HPs and eMachines have software preinstalled that will make recovery/restore CDs. I don't recall the exact name of the program but it's on the Start Menu somewhere. eMachines require six CDs or one DVD. I think HPs require six CDs. Once you get the computer restored to factory settings, before you do anything else, make those recovery disks....someday you'll be glad you took the time.
