HOW TO SOLVE NON SYSTEM DISK OR DISK ERROR ( ONLY DISPLAY C:c>, MISSING OPERATING SYSTEM )

Solution: 

1. First, you can restart by copying the system of  Bootable or Floppy/CD and keeping it on the Hard Disk.
2. Secondly, you can solve it by detecting Hard Disk.
3. You can format hard disk.
4. If the above tips don't work, it will be better for you to change  the Hard Disk.