By "reboot" you mean "reimage". Reboot does not mean what you think it means.
It should have a recovery partition on the hard-drive you can get to from the boot menu. Look in the manual how to restore it. If you wiped it somehow, you can make a USB setup of XP. http://reboot.pro/topic/4900-install-xp-from-usb/
Or buy an exteral cd or dvd drive to use.