Comment 14 for bug 86666

I haven't done it myself, and information on the net is scarce. I found out that following could be added to /boot/grub/menu.lst:
# Setup serial (COM1) here with baudrate 9600
# use --unit=1 (for COM2) and so on
serial --unit=0 --speed=9600

# Now setup terminal as both Serial Line(/dev/ttyS0) and
# Monitor Console(/dev/tty0) depending upon where you press key
# with in timeout (15 sec) period. Otherwise first entry
# (console(Monitor)=>tty0) is selected here.
terminal --timeout=15 console serial

Then a boot line something like:
kernel /boot/vmlinuz-2.6.17-11-386 ro root=/dev/sda3 console=ttyS0 console=tty0

Found from Google cache with search terms 'serial console boot kernel', and the instructions were for the 2.4 kernel.

With the laptop connected to the feisty computer, you should run something like minicom to listen to the serial port (though if you haven't used it before, the user interface is quite terrible).

Here's some newer tutorial: http://www.howtoforge.com/setting_up_a_serial_console