We have a maxtor basics

Question

we have a maxtor basics external hard drive. We run vista and the new microsoft office 2007. The problem is that the laptop is not recognising the external. We open my computer and even though it is plugged into a port it does not show up. When i tried to save to it a message tells me it is not accessible. We have saved on this external before and now it won't work.PLEASE HELPCARMEL