Your router will have the option to disable the SSID in it's firmware. Erasing it essentially renames it to _____.
When they say you will have to enter it in manually, it's an issue you will have to deal with in your computer, not your router. They mean that your laptop will not pick up the name automatically through the "View Available Networks" window, or whatever your wireless utility calls it. If the computer in question has never been on the network, or that particular profile (called "Preferred Network" in XP) is erased from it, you will have to type the SSID into the appropriate bar when you create that profile in your wireless utility.