Remove the non-system disk from your boot device. For example, remove the non-system disk from the CD-ROM drive. If there is no CD in the drive then try to
Change your computer's boot sequence. To do this, you must change your computer's setup and the option that controls which device your computer uses to start from. Make sure that you select a device that has boot files (or operating system files) installed.
If you start your computer from a hard disk drive, install a bootable operating system (such as Windows XP) on the drive.
If you know that there is in fact an operating system installed on the drive, it's possible that the OS has been corrupted , the hard drive has failed, or the hard drive controller has failed.
you can also check in BIOS and see if in fact your Hard drive even shows in BIOS. if not, it's probable the drive is failed.