You may find the quickest way to do things is:
install XP on first hard drive
insert openSUSE CD/DVD and proceed to installation
look what openSUSE is suggesting - my guess is that it will suggest taking over the second hard drive; if so
enable booting from MBR
enable /for bootloader
If not, review the suggestions above and edit the installation to make it do what you want in the light of the suggestions above.
You can always abort the installation and start again/ask more questions if you need to but you may save yourself a lot of trouble by seeing first what openSUSE is proposing to do and accepting that if it is what you want.