0x99: Invalid Second Stage Mismatch between drive and BIOS geometry, or a bad map file. Some evidence that LINEAR needs to be set on the disk (see LiloNotes)
1. Maybe try specifying the option:
linear
in lilo.conf
2. Maybe try uninstalling lilo and reinstalling.
3. Maybe try flashing your BIOS.
4. Try enabling LBA in the BIOS.
If you can do 4 try that first. Don't know much at all about this though.
original here.