i still need version ocf slack to be specific.
and ofcource knowing your keyboard, screen, graphcard spec would help even more.
i could then give you a step by step.

keyboard;;
what layout=?
language=?

screen;;
horisontal sync=?
vertical refresh=?
type=? (lcd, crt, tft, tv...)
how many collors (2, 4, 8, 16, 24, 32bit collor)
what size? 1024x768...
below you have the codes that lilo uses for framebuffer
Code:
#   Colours   640x480 800x600 1024x768 1280x1024 1600x1200
#  ----------+---------------------------------------------
#  256       |   769     771      773      775       796     | 8bit
#  32,768    |   784     787      790      793       797     |16bit
#  65,536    |   785     788      791      794       798     
#  16.8M     |   786     789      792      795       799

graphcard;;
chip=?
model=?
maker=?
memory=?
if you know all these you can run xorgconfig and put the values where they are asked for.
if not, hmm, have you gotten knoppix to run from CD on that computer?