I find my hdisk can't work the day before , when my computer boot to
the step
of loading OS , the screen is black and freeze. and I hear hdisk makes
sound much
like that of  launching  engine (only much less louder) which I feel it may

try to find Main Boot Record (MBR) and fail .The sound mentioned above
lasts and
lasts .

     Then I boot from a floppy disk into DOS 6.22 , run DEBUG .
debug<enter>
F 200 L200 0<enter>
a 100<enter>
mov ax,301<enter>
mov bx,200<enter>
mov cx,1<enter>
mov dx,0080<enter> (0081 for second drive, 0082 for third....)
int 13<enter>
int 3<enter>
<enter>
G=100<enter>

it doesn't show any write error. afterwards I run fdisk to define
the primary partition ,though just then the hdisk make sound (just
as I mentioned above )again and again untill the computer loop to
dead .Just at this time , I find a interesting phenomena : I do a
warm startup , the CMOS can't detect the hdisk . only can it detect
the hdisk after cold startup.

All this may prove my hdisk get a 0 cylinder BAD or mechanic & electric
deformation.
any ideas ?

Yours
David Dwell