One thing that will help you considerably is next time you are in Suse put a # in front of the line "fgxmenu" in /boot/grub/menu.lst. This will disable graphic screen of Grub but at the time gives you back the option of a Grub prompt.
When you reboot again the bottom of the Grub menu will have an option to press "c". That will give you a Grub prompt with which you can boot up XP manually.
It is so easy if you know which partition. If XP is in the first partition of the first bootable disk it is known to Grub as (hd0,0), as Grub counts from 0. At a Grub prompt you can ask Grub to show you the partitions of 1st disk (hd0) by
if XP partition, type ID 0x7, is in partition 0 you can type these lines to fire it up manually