I'm going to guess that SuSE didn't detect windows for some reason but did install grub and your booting by somehow forcing each hard drive OR that you can't boot XP (not that you'd want to obviously.)
I'd say have a look in the SuSE control setup, let it have another scan for other OSs on your computer and see if it finds windows. If not then you will need to manually add the windows install, it should be pretty easy to find some examples out there of what to put.
Then Grub should give you the option of SuSE or Windows each boot. Remember to set SuSE as default