If by what you type, do you mean, when you open up my computer and you do not see the CD drive icon? If that is so, it may mot recognize the drive, the drive my not have power attached or the cable may be disconnected from the mother board or the CD Drive. If there is proper power and the cables are connected and the drive still does not show then one way to check is by going into device manager. (I'm trying to do this by memory) It should be under: Control Panel > Administrative Tools > Device Manager. When you open it, there should be a list of many items including drives, cpu, ethernet port...ect, open the one for CD drives and see if it shows the drive there. If it does show the drive, then near the top pf the window is the icon to disable/enable the device. Disable the drive than enable it. Try and see if it then recognizes the CD drive.
If you mean that it isn't reading the CD, then it might be a bad drive, a CD that isn't compatible, or the CD is unreadable (i.e. has too many scratches).