I had the same problem and could not solve it until today (look at my posts). I gave it up because I think it's impossible to make a real install using a new laptop, might be a driver problem (SATA, SCSI).
But now I think no one needs the real install. Take the howto from ziplock to make the live install and make your own changes by adding one or more .lzm modules in the directory /bt/modules. You can look here in the forum for .lzm modules or on the slax site and search for modules (ending ...mo), convert them to .lzm (using mo2lzm) an drop them into /bt/modules.
If you want to store your personal settings use the command:
dir2lzm /mnt/live/memory/changes changes.lzm
and move the changes.lzm to /bt/modules
For more changes use a new name (e.g. changes1.lzm).