Your confusion is most probably a question of names: C, D, and E etc are Windows conventions, not Linux. You don’t say whether your drives are actual physical drives or partitions, but I assume the latter. The thing to do is to check in Windows what the exact sizes of the “drives” (partitions) are, and which one is empty. Write that down, and this information should enable you to figure out which of the partitions turning up in the openSUSE install routine is the one referred to by Windows as “D”, ie. the one you want to install on. If I remember correctly, openSUSE is most likely to choose an empty partition as its installation target anyway.
You had me confused there: I just replied to an identical message in boot/installand thought my reply had disappeared into thin air… Don’t ask the same question in several topics please.
I’ve just replied to your private message - which I found (because of the email notification) before I found this. It is generally better to keep these issues on the forum, so that other can learn from it. Feel free to send me another private message if the instructions I gave you don’t work (and I promise to reply) but I’d prefer to do this via the forum - if only so that others can correct me, or suggest better alternatives…