The above behavior generally means that the significant data is either missing or corruption in VBR (Volume Boot Record). The volume boot record contains operating system specific information for format of the specific hard drive
partitions. If this data area is damaged, by controller failure, virus infection, improper system shutdown etc., then Windows cannot access the hard drive.

The general response of the “Missing operating system” error is – try to boot your system through a floppy disk and re-partition the hard drive (possibly using the FDISK tool). This method, thereby completely removes the probability for any sort of recovery of your precious data. You can try out the rebuilding VBR to resolve this behavior. cmveletrhy.