I don't have a cure for this but the obvious thing to do is to tell the Bios not to change the disk order for the first 2 disks and so the 3rd disk, controlled by PCI-IDE, is in the 3rd position of the booting order if it is added. This way you have the two original systems booting normally and only need to add PCLos to the menu.lst of Ubunu.
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I found no solution to the earlier GRUB mod. So I'm tryin' now to import the PCLOS loader into the Ubuntu GRUB (with XPPro), but alas, no success thus far.
PCLOS disk is now mapping as hd2. From GRUB cli, I did find /boot/grub/menu.lst. It returned 3 entries: (hd0,0[Ubuntu]), (hd2,0), and (hd2,6).
sudo su
grub
geometry (hd0)
geometry (hd1)
geometry (hd2)
No everybody is aware of your setup. Since you are able to boot 2 out of the 3 systems you should freeze the disk order from now on and concentrate on working with the Ubuntu's Grub.
The easiest way to multi boot as many distros as you want is during installation you point a gun at the installer's head and instruct it not put its boot loader in the MBR but inside its root partition. If that root partition is say (hd2,8) then the Grub commands to boot it are
Code:
title whatever OS in (hd2,8)
root (hd2,8)
chainloader +1
or if the distro has Grub the following also works
Code:
title whatever OS in (hd2,8)
root (hd2,8)
configfile /boot/grub/menu.lst
The above is all you need to boot as many distros as you care to install.
Believe me there is nothing difficult in booting with Linux. You can write your own menu.lst even before you install all your operating systems. "Chainloading" is the easiest and laziest way. It is exactly how a MS Windoze is booted so why not use it.