Missing Operating System

when starting up the computer, i get the error
"Missing Operating System"
(see question "boot up" on 6/7/98 for more info)


According to documentation on the net, this error occurs
when the boot record signature of the master boot
record does not match a certain value at a certain location.
In this case, the boot sector is invalid and the computer cannot boot.
This error can also occur if there is no active partition defined
in the partition table.


so i start the computer using a bootable MS-DOS disk that contains
Fdisk.exe, Format.com, Sys.com, and Scandisk.exe

i use Fdisk.exe to view the partitions on the hard disk.
i select option 4 (Display partition information).

one partition is listed, and it is defined as active
(uppercase A in the Status column.)

then i run the SYS command

i receive the error:

Invalid media type reading drive C
Abort, Retry, Fail?


then i run:

scandisk c:

and get the error:

Scandisk cannot examine drive c:

what next?