No hard disk recognition---HELP!!

[Mark Davis]

In article <451 at ntcsd1.UUCP> dmc at ntcsd1.UUCP (David Clemens) writes:
> ...
>   I am working with a PS/2 Model 80 computer running Xenix 386. The system 
>has a 115M hard disk of which 20M is in a DOS partition.
> ... when I took
>the disk out and again tried to reboot, the computer came up in IBM BASIC.
>(IBM BASIC boots up from memory when a the computer has no other operating
>system installed)

Apparently David's spool directory is full because mail bounces with
	"mail: cannot append to /usr/mail/dmc"
but this may be of general interest anyway, so I will post:

It sounds to me like the "master boot record" on your hard disk got
blown away.  The master boot record is on cylinder 0, head 0, sector 1
of the hard disk.  It contains (amoung other things), the name of the
operating system that you used to partition the disk, some boot code
(that nobody explains) and the partition table.

When the computer boots, it reads the master boot record, does some
magic with the boot code and interprets the partition table to find out
where there is an OS to boot from.  Then it goes to that partition, and
reads the first record that boots the rest of the OS.

If you boot DOS from a floppy, some but not all of the information in
that record must be used.  For sure you need the partition table.  I
think DOS actually gets most of its geometry information from the BIOS
tables (some interrupt vectors set by the BIOS ROM boot code), so it
may not need anything else in that record.

It sounds to me like your Computone disk blew away part, but not all of the
master boot record.  To restore it, there are two possibilities:
	1. run FDISK again (which will destroy data on the disk)
				OR
	2. Get a good hard disk recovery program and try to fix the
	   master boot record.

If there is important data on the disk, you really have to try 2, but
it will be very time consuming for you to figure out what you are doing
and then fix it.  I would recommend that you start by getting the Paul
Mace Hard Disk Data Recovery book.  You will also benefit from using a
utility like Norton's, but I believe you may be able to fix it with
debug.

Based on the information that you posted, I would estimate that getting
the information and programs, learning enough and then doing the fix
would require about 6 man hours.  If the data is not critical, it must
be possible to Nuke the disk (run FDISK) and re-install everything from
the ground up in less time than that.

I live in Durham (489-0157) and work in Chapel Hill (962-1739), so feel
free to call if you have further questions.

Hope this helps - Mark (davis at cs.unc.edu or uunet!mcnc!davis)