Open your baldur.ini, under [Alias]:
HD0:=C:\Program Files\Black Isle\Baldur´s Gate
CD1:=C:\Program Files\Black Isle\Baldur´s Gate\
CD2:=C:\Program Files\Black Isle\Baldur´s Gate\
CD3:=C:\Program Files\Black Isle\Baldur´s Gate\
CD4:=C:\Program Files\Black Isle\Baldur´s Gate\
CD5:=C:\Program Files\Black Isle\Baldur´s Gate\
CD6:=C:\Program Files\Black Isle\Baldur´s Gate\