I have 3 physical disks on my system. The initial disk was a 250GB SATA disk with an OEM windows xp system. I installed ubuntu (several versions from feisty on up to the current 8.10 64 bit system) on a SCSI disk and dual booted just fine from there. I recently added a 500 GB SATA disk and installed 8.10 64 bit there to do some vmware server stuff. The initial loader that the BIOS is pointed at is on the 250 GB SATA. It points to the 36 GB SCSI. When I rebooted the first time after installing 8.10 on the 500 GB SATA the newly installed OS was not available in grub - just the entries for ubuntu on the scsi disk and windows on the SATA 250 disk. So, I mounted the 500 GB disk in /mnt/oldsys on the running system (on the SCSI disk). I copied the needed entries from /mnt/oldsys/boot/grub/menu.lst to /boot/grub/menu.lst. I also copied the required boot files into /boot/grub. When I added the entries in menu.lst, I added descriptive locations to the titles so I could tell what disk/system I was booting. That is the current situation and when grub comes up I have the option to boot from either of the 3 disks. This is pretty convoluted since to get to the (default) 64 bit 8.10 on the 500 GB disk, the bios goes to the 250 GB SATA, picks up the initial loader which transfers to the 1.5 (I think) loader on the 36 GB SCSI disk which gets me to it's menu.lst and boots the kernel with the needed info locally and then finishes bringing up the OS on the 500 GB SATA. However,... at some point I want to replace the SCSI disk with a 500 GB SATA (the box has 3 slots for disks in the drive enclosure). Replacing the disk in the middle of the boot sequence, would, I presume, be disastrous. What do I need to do to point the initial loader on the 250 GB SATA to the 500 GB SATA instead of the 36 GB SCSI? Or, alternatively, if I configure the bios to initially boot from the 500 GB SATA, can I then set up grub to allow me to get to any of the systems/disks from /boot /grub/menu.lst on the 500 GB SATA system. Detailed steps/howtos would be very much appreciated.