@AL|EN so I did as you said, but ran into a peculiar problem...
I own SoD via GOG, where it is sold as a DLC for the bg1 enhanced edition. And there, as far as I can tell, it is already integrated into the main game as a patch.
Therefore I don't have the Siege of Dragonspear path the installer asks for... did I do something wrong?
I have respective paths to BG:EE, BG:EE with SoD, BG II: EE, as well as BG II: EE for EET.