I make a large box and then click CURVE ----> Cylinder and it makes a cylinder. I then go to CURVE ---> THICKEN and it appears as though it makes it hollow. I then proceed to press ESC to deselect it and it disappears.

What has happened? Thanx for any help!

Does anyone know how? I think a few people around here need to know how to? Thanx to anyone that answers

You probably don't have 'show curves' selected in the view->show menu. Make sure it has a check mark by it. Either that or the camera in the editor is too far away from the cylinder - stuff that's far from the camera tends to get clipped for speed reasons. If this doesn't help I don't know what your problem is...