diff -r fdb4b5ab8099 src/newgrf_gui.cpp
--- a/src/newgrf_gui.cpp	Sun May 23 11:30:13 2010 +0200
+++ b/src/newgrf_gui.cpp	Sun May 23 13:10:45 2010 +0200
@@ -187,6 +187,7 @@
 	bool execute;               ///< On pressing 'apply changes' are grf changes applied immediately, or only list is updated.
 	int query_widget;           ///< Widget that opened the last query.
 	int preset;                 ///< Selected preset.
+	int active_over;            ///< Active GRF item over which another one is dragged, \c -1 if none
 
 	NewGRFWindow(const WindowDesc *desc, bool editable, bool show_params, bool execute, GRFConfig **orig_list) : QueryStringBaseWindow(EDITBOX_MAX_SIZE)
 	{
@@ -199,6 +200,7 @@
 		this->execute     = execute;
 		this->show_params = show_params;
 		this->preset      = -1;
+		this->active_over = -1;
 
 		CopyGRFConfigList(&this->actives, *orig_list, false);
 		GetGRFPresetList(&_grf_preset_list);
@@ -361,6 +363,12 @@
 						PaletteID pal = this->GetPalette(c);
 
 						if (h) GfxFillRect(r.left + 1, y, r.right - 1, y + step_height - 1, 156);
+						if (!h && i == this->active_over) { // Higlight the destination of the dragged NewGRF file.
+							uint active_sel_pos = 0;
+							for (GRFConfig *c = this->actives; c != NULL && c != this->active_sel; c = c->next, active_sel_pos++) {}
+							uint top = (((uint) this->active_over) < active_sel_pos ? y + 1 : y + step_height - 2);
+							GfxFillRect(r.left + WD_FRAMERECT_LEFT, top - 1, r.right - WD_FRAMERECT_RIGHT, top + 1, 156);
+						}
 						DrawSprite(SPR_SQUARE, pal, square_left, y + sprite_offset_y);
 						if (c->error != NULL) DrawSprite(SPR_WARNING_SIGN, 0, warning_left, y + sprite_offset_y);
 						uint txtoffset = c->error == NULL ? 0 : 10;
@@ -691,6 +699,33 @@
 		}
 
 		ResetObjectToPlace();
+
+		if (this->active_over != -1) {
+			/* End of drag-and-drop, hide dragged destination highlight. */
+			this->active_over = -1;
+			this->SetWidgetDirty(SNGRFS_FILE_LIST);
+		}
+	}
+
+	virtual void OnMouseDrag(Point pt, int widget)
+	{
+		if (this->active_sel != NULL && widget == SNGRFS_FILE_LIST) {
+			/* An active NewGRF file is dragged… */
+			NWidgetBase *nw = this->GetWidget<NWidgetBase>(widget);
+			uint active_to = (pt.y - nw->pos_y) / nw->resize_y + this->vscroll.GetPosition();
+
+			uint active_sel_pos = 0;
+			for (GRFConfig *c = this->actives; c != NULL && c != this->active_sel; c = c->next, active_sel_pos++) {}
+
+			if (active_to >= this->vscroll.GetPosition() &&
+					active_to < (uint) min(this->vscroll.GetPosition() + this->vscroll.GetCapacity(), this->vscroll.GetCount())) { // …over an existing NewGRF file.
+				this->active_over = active_to;
+				this->SetWidgetDirty(widget);
+			} else if (active_to != active_sel_pos && this->active_over != -1) { // …outside of the NewGRF file list.
+				this->active_over = -1;
+				this->SetWidgetDirty(widget);
+			}
+		}
 	}
 
 	virtual void OnDropdownSelect(int widget, int index)