Perhaps you might want to change this back to
for starters - ie instructing LILO to re-install on the MBR
once you've made the change, then run
to re-install the loader and new map.
( edit it in an xterm with gedit or kedit )
If this works to boot back into Slack normally from the hard drive, then put your old Win entry back in and again run /sbin/lilo afterwards