In an empty column enter a formula.
=A1 & B1 & C1 & D1 entered in E1
Drag/copy down column E
If you want spaces between use
=A1 & " " & B1 & " " & etc.
When happy, select column E and Copy then Edit>Paste Special(in
place)>Values>OK>Esc
Delete A through D
Gord Dibben MS Excel MVP