If you can't get past the bootloader then it's probably to do with the floppy drive speed. Set that to "100% compatible" and also make sure "cycle exact" is ticked in the chipset options. The demo also uses 1MB of ram, so make sure an extra 512KB is added somewhere (should be fine with chip, slow or fast)
PS. Yes, many of us were employed at Core Design, but I left just as Tomb Raider went into pre-production.