The problem could be that:
(a) lilo can't access past 1024
AND/OR
(b) the BIOS can't access past 1024
If the latter then you don't really have much choice except replacing the MOBO (or putting the /boot partition at the front of the hard drive.
The former is MUCH more likely...
Just boot from a Linux boot floppy, log in as root, edit the file /etc/lilo.conf, in the top section (before the first section starting image=) add a line:
Then run /sbin/lilo