Henrik mentions the "-boot-load-size 32".
I think even on my 2003 1GHz computer, I had to use the smartbootmanager
program (I forget the exact name but it used to be on the SLackware
release, somewhere) to boot from the CD or DVD. Put the bootmanager on
a floppy disk, and then boot from the floppy disk, which in turn allowed
one to boot from the DVD.
This was an issue, and for a long time Slackware used some old standard so
old hardware could boot the disk. Then eventually that was changed (I
forget at which release) so we had to boot other ways with old hardware,
or get new hardware.
This is hazy because I can't fully remember, but I'm pretty sure I had to
use the smart boot manager until I moved to this 3GHz computer last
OCtober.
It has something to do with the BIOS not being able to read larger boot
images or something, it was discussed on the changelog at one point, was
discussed here, but years back so I can't remember details.
You could move the needed things to a USB flash drive, boot from that
(assuming your computer can boot from USB) then once the installer gets
going, point it to the pacakges on the DVD, and that should work.
Michael