To configure a dual boot, you need to edit the menu.lst from the grub. this file is missing in Ubuntu 9.10. is there any other way to configure the boot menu?? i tried the steps mentioned in the documentation to configure n change the default oprating system

it uises grub2 which doesnt use menu.lst

It uses scripts and files to generate /boot/grub/grub.cfg

You can manually edit the file but next time update-grub is ran the changes will be lost so you need to add the changes properly in grub so they are persisitant

This will help:
https://wiki.ubuntu.com/Grub2

Its a bit hard to get your head around but you'll get it eventually

Do I understand correctly that both installations are correctly recognized by GRUB but that you only want to change the order of preference?

You can do this by editing /etc/default/grub
Change the line:
GRUB_DEFAULT=0

and replace 0 with n-1 (where n is the row in which your preferred boot entry is)

If you really need to add entries, you would have to edit /etc/grub.d/40_custom, but for actual code... please follow the mentioned manual :-)

Do I understand correctly that both installations are correctly recognized by GRUB but that you only want to change the order of preference?

You can do this by editing /etc/default/grub
Change the line:
GRUB_DEFAULT=0

and replace 0 with n-1 (where n is the row in which your preferred boot entry is)

If you really need to add entries, you would have to edit /etc/grub.d/40_custom, but for actual code... please follow the mentioned manual :-)