I have all my games on my B drive, Kingmakersetupexe does not seem to recognize that fact. I need that program to get on to NWN multiplayer- anyone have the same problem and (perhaps) a solution?

You could try reinstalling it and putting it into another folder, eg. the default B: GOG Games/NWN

Otherwise try contacting the GOG support, they tend to be quick.

Could you be more specific about the problem? Is Kingmakersetup not detecting your NWN install at all, is it not allowing you to select your B drive to install to, or does it abort when told to install to B, for example?

If it is not allowing you to select B (this was used for the second floppy disk on IBM computers, which is why hard disks use C by default), then a workaround might be to create an NTFS junction from another drive (this could be a temporary one like a USB stick) to your NWN folder on B, then tell the installer to use that junction (anything written to it will be redirected to the B drive then).

Link Shell Extension is a free utility for creating such junctions.