Extruding along a path

I have added a Bézier curve and a Bézier circle, once I have got the tube extruded along the curve how do I get rid of the circle, when I try to delete it the tube also gets deleted.

so here it is: select your tube, alt+c, mesh from curve.
but you won’t be able to edit it by the curves anymore

Change the curve circle from “2D” to “3D” under the curve properties, this will remove the fill of the curve circle and it will not be visible.

http://www.pasteall.org/pic/show.php?id=4891

Thanks to you both.