B:\ is (or was) usually either the second floppy drive, if the PC had two, or the same floppy drive as A:\, but DOS would prompt you for the other floppy disk if you specified B:.
But now you are saying B:\ is your pendrive? Can you access files on the pendrive from a command shell (i.e. a "DOS prompt" window)? That is, if you type the command
dir B:\
does it show you the files there?
If B:\ is awkward to use, the DOS
SUBST command may be useful for you. That is, if you want it to access files in C:\ZONEFILES instead of B:, you could use this command:
subst B: C:\ZONEFILES
Then any program or command that accesses B: will really access C:\ZONEFILES.