Are you using the Windows bootloader or are you booting XP from within Ubuntu (from the Ubuntu grub screen)? If you are booting XP from Ubuntu grub, can you print out your /boot/grub/menu.lst here? You just might have to fix the entry for Suse. The Ubuntu install is usually good at recognizing what distros are present during install, you just might need a tweak. If you can, also tell us what partition your /boot is on for Suse.

I agree with GoinEasy9, the problem isthat the ubuntu bootloader overwrote the Suse bootloader and unfortunately didn't auto-detect Suse. Once you past your menu.lst and tell use what partition Suse is on we can help you to rewrite your menu.lst file to add a Suse entry.

Since you have not given the suse partition number we cannot guide you to completely correct this, but here are some basic steps that should get you most of the way.

1. Make a new directory in ubuntu named /boot/suse
2. Mount your suse partition on your system
3. copy the files from your suse boot directory into /boot/suse
4. Copy the following lines into your menu.lst file, substituting the values in {} with the appropriate values for your suse installation.

title SUSE
kernel /boot/suse/{suse vmlinux file} ro quiet splash
initrd /boot/suse/{suse intrd file}
quiet