Installed a new hard drive

Well, since the new hard disk is not formatted, and there is nothing currently on it, you will not get a dos prompt or an operating system detected. What you need to do is insert your Windows XP disk, then reboot the machine. When you see the HP screen, tap the F12 key, which will take you to a boot menu. On the boot menu, choose your CD drive, then the computer will boot from the windows disk. From there, just format your disk, and install Windows.