[GTALUG] Cannot open rescue disk

[Ken Heard]

The computer has Debian Jessie installed in it.  One day recently after 
starting it, the BIOS identified the hardware.  It went as far as to 
display the line "Verifying DMI Pool Data ..................." and then 
stopped. The rest of the monitor was filled up with series of 99s

I then tried to use a the Rescue mode on a Stretch net install disk. 
The opening menu of the disk appeared on the monitor, but it did not 
respond to input from the keyboard.  I consequently could not select the 
rescue option.

I checked the keyboard on another computer where it worked.  Using the 
keyboard from the other computer on the one not working also did not 
work there.

The net install disk can be opened on the other computer.  In fact I 
used it there to install Stretch on it.

I did a Google search, but all the references I found assumed ability to 
open the computer from a rescue disk.

Does anybody know why this problem would arise, and what to do about it 
-- if anything -- by way of fixing it.

Regards, Ken Heard